Fy Project: Data Aquisition

Final Project Report of BE (IE) Year 2007

PR –15b- IIEE – 438 – 2007

MIDAS Multiplexed Industrial Data Acquisition System Using NI LabVIEW

M. Ubaid Khan Kamali

(1526)

Rizwan Ahmed Khan

(1530)

Sikander Ali

(1534)

Syed Wasif Ali Shah

(1538)

Submitted to In-charge Final Project Work

Ashab Mirza Associate Professor IIEE

I

SUPERVISORS OF THE PROJECT

External Project Supervisor

Mr.Farhan Khan

Assistant Professor, PNS Jauhar (NUST), Karachi MS (Communications) NEDUET, Karachi BE (Industrial electronics) NEDUET, Karachi Email: [email protected]

Internal Project Supervisor

Mrs. Quratul Ain

Lecturer, IIEE BE (Industrial Electronics) NEDUET, Karachi Incharge ICI Lab at IIEE Email: [email protected]

Project Work Incharge

Mr. Ashab Mirza

Associate Professor, IIEE MS (Aerospace Engg.) ENSAE, Toulouse, France BE (Electronics) NEDUET, Karachi Email: [email protected]

Multiplexed Industrial Data Acquisition System (MIDAS)

TEAM MEMBERS

Syed Wasif Ali Shah (Group Leader)

Cell: +92-321-2185029 Email: [email protected]

Rizwan Ahmed Khan Cell: +92-331-3143364 Email: [email protected]

M. Ubaid Khan Kamali Cell: +92-300-3087561 Email: [email protected]

Sikander Ali Cell: +92-0301-2880070 Email: [email protected]

II

Enrollment No.

House # A-368, Ward # 4, Majeed Shah Street, JHUDO, District Mirpurkhas-Sindh

IIEE-615

House # 314, Wapda Colony, T.P.S, Guddu, District Kashmore-Sindh

IIEE-607

House # 512, behind Police Station. District Tando Adam-Sindh

Unit # 1, Near Meat Market, P.O Bhiria Road, District Naushehro Feroze-Sindh

IIEE-603

IIEE-611

.

__________________________________________________________________ PCSIR - Institute of Industrial Electronics Engineering, IIEE ST-22/C, Block-6 Gulshan-e-Iqbal, Karachi – 75300

III

Acknowledgment

During our project work Associate Professor IIEE Ashab Mirza helped us all the possible ways. He guide us in getting

the most suitable data acquisition card, the

application software for HMI and also gave technical information about DAQ card and signal conditioning. We are indebt of Dr. Syed Naimat Ali Rizvi; Principal IIEE allowed the purchase of data acquisition card and solving our problems. Engr. Farhan Khan, Ex. Lecturer of IIEE, who provide us technical help in designing digital scanner using microcontroller. Engr. Farah Haroon, Assistant Professor of IIEE, provided us the strong basis of electronic devices, circuits and systems. We are also thankful to Engr. Azmat Sher, IIEE graduate and CEO Industronics which provides industrial solutions to various control systems, helped us in developing the mechanical hardware and indigenously designed DAQ card, which was used before purchase of NI DAQ card. Engr. Tehseen Jabbar, BE Electronics, helped us in managing project work that only with their help and untiring guidance; we are able to turn this project into reality.

IV

PREFACE At this auspicious occasion when we are submitting the project report on “Multiplexed Industrial data Acquisition System Using National Instrument’s LabVIEW”, we ourselves highly indebted towards Allah Almighty Who enabled us to complete this project in due time. We choose Multiplexed Industrial Data Acquisition System as a final project because it was the most important instrumentation project. It is a complete industrial Virtual Instrumentation system, which is the future of industrial automation. For this purpose the NI multifunction DAQ card was employed. This project contains the three most important quantities of any process industry as demo which are level, temperature and servo valve position. Besides data acquisition card this project also contains the signal conditioning of different transducer and also hardware display for input quantities. This project contains certain complexities and one can learn a lot from this project. The report consists of seven chapters in all. First chapter gives introduction which includes the project need, problem description, block diagram and schematics with description of each block and part, all possible solutions of problem and description plus reason of that solution which we selected. Second chapter contains analysis and simulation which includes the mathematical models of system and sub-systems, theoretical solution and its performance analysis and computer simulation of those subsystems for which simulation was possible on available software. Third chapter describes mechanical model which includes industrial prototype development for the selected parameters.

Fourth chapter describes

sensor’s selection and signal conditioning which describes different sensors available and advantages of selected sensors and their signal conditioning. Fifth chapter is on digital scanner which includes its designing techniques and features and describes its importance in industry. Sixth chapter describes the configuration of DAQ card. Seventh chapter gives human machine interface developed on LabVIEW, its graphical programming and describes its features and advantages. The conclusion

V includes the points which we learned during the designing of this project and it also includes the possible recommendation. During designing of this project we faced many difficulties. Most problems were related to unavailability of required electronic devices. So we had to complete this project with available technology as well as employed the latest virtual instrumentation techniques. As industrial transducers are very expensive so transducer’s arrangement was also a problem but we designed transducers ourselves as well. They were manufactured on industrial standard quality and were linear with respect to physical quantity. In the end we would like again to express our gratitude towards ALLAH almighty, then our parents who are constant source of encouragement and our teachers for their efforts to make us acquainted with the electronics and control and most of our Institute the IIEE which provide us the platform to become the practically oriented engineers. Karachi January 3rd, 2008.

VI

LIST OF FIGURES Figure-1.1: Traditional instruments (left) and software based virtual instruments (right) largely share the same architectural components, but radically different philosophies [Courtesy NI website]. Page # 3 Figure-1.2: Virtual instrumentation combines productive software, modular I/O, and scalable platforms. [Courtesy NI website], Page# 5 Figure-1.3: LabVIEW is a leader in application software used in PC-based data acquisition and instrument control. [Survey of Design News and R&D Magazine, QI 2004], Page# 7 Figure-1.4: A PC based data acquisition [Courtesy National Instrument Website], Page#8 Figure-2.1: Thermal System Block Diagram, page # 13 Figure-2.2: See Back Effect, page # 14 Figure-2.3: A simple thermocouple, page # 16 Figure-2.4: Physical circuit for thermocouple, Page # 17 Figure-2.5: Conceptual T(x) plot of thermocouple, Page# 18 Figure-2.6: Cold junction compensation, Page# 20 Figure-2.7: A general block diagram for position control, page# 21 Figure-2.8: Graph between generated voltage and applied RPM, page# 23 Figure-2.9: Graph between generated and voltage, Page# 23 Figure-2.10: Graph for J-Type Thermocouple, page# 25 Figure-2.11: Open loop impulse response, page# 26 Figure-3.1: Mechanical model for liquid level system with inlet pump motor, page# 29 Figure-3.2: Electric furnace surrounded by wooden block for safety and protection attached with the temperature controller. The controller is based upon SCR pulse firing technique, page# 30 Figure-3.3: Servo controlled valve mechanism to control the outlet flow of liquid tank , page# 31

VII

Figure-3.4: Overall mechanical assembly, page# 32 Figure-4.1: Graph between transmitter output and height of level, page# 37 Figure-4.2: Block Diagram of Level Transmitter Signal Conditioning, page # 38 Figure-4.3: Circuit Diagram of Level Transmitter Signal Conditioner, page # 38 Figure 4.4: Graph between temperature and RTD Output, page # 39 Figure-4.5: Graph between AD594 output voltage with respect to temperature, page# 40 Figure-4.6: Block Diagram of Thermocouple Signal Conditioning Output, page # 41 Figure-4.7: Circuit Diagram of Thermocouple Signal Conditioner, page # 42 Figure-4.8: Block Diagram of PI Controller for Controlled Valve, page# 43 Figure-4.9: Graph of feedback signal from pot meter against valve position, page# 44 Figure-4.10: Circuit Diagram of proportional controller for the servo controlled valve position, page # 45 Figure-5.1: Block diagram of digital scanner, page# 51 Figure-5.2: Circuit schematic of digital scanner, page# 52 Figure-5.3: Controller Program flowchart, page# 55 Figure-6.1: The block diagram of indigenously developed DAQ card. The parameter to be processed and displayed will be selected by the controller from select logic, page# 60 Figure-6.2: Circuit schematic of indigenously developed data acquisition card, page # 62

Figure-6.3: : NI USB-6008 multifunction DAQ card, page # 64 Figure 6.4: The block diagram of NI SUB-6008 multifunction DAQ card, page # 65 Figure-6.5: Setting up hardware, page# 66 Figure-6.6: Device recognition tree in max, page # 67

VIII Figure-6.7: : Device self test. A success message will be displayed if device pass the self test as shown, page # 68 Figure-6.8: Attaching sensors/signal lines with the device to the selected channels and setting up timing and triggering from software, page# 69 Figure-7.1: Screenshot of a simple LabVIEW program [Courtesy of NI website], page# 72 Figure-7.2: Data acquisition task in LabVIEW [courtesy NI website], page # 74 Figure-7.3: DAQ assistant express VI, page # 75 Figure-7.4: DAQ device physical channels configuration window, page# 76 Figure-7.5: The front panel of developed HMI on LabVIEW, page# 78 Figure-7.6: Block diagram programming of developed HMI using LabVIEW Gprogramming environment, page# 80

IX

LIST OF TABLES Table-2.1: Readings for generator action. Applied RPM and generated voltage, page# 22 Table-2.2: Readings for generator action. Applied and generated voltages, page# 22 Tabel-4.1: Level Transmitter output table during Calibration, page# 37 Table-4.2: RTD's measured values, page# 39 Table-4.3: AD594 output voltage with respect to temperature, page# 40 Table-4.4: Valve position and feedback signal, page# 43

CONTENTS Title Project Supervisors

………………………………………………………………

I

Group Members

…………………………………………………………

II

Acknowledgment

………………………………………………………………

III

Preface

…………………………………………………………

IV

List of Figures

…………………………………………………………

VI

List of Tables

…………………………………………………………

IX

1. INTRODUCTION

[1-11]

1.1 Instrumentation

…………………

2

1.2 Traditional Versus Virtual Instrumentation

…………………

2

1.3 Virtual Instrumentation in the Engineering Process 1.4 Data Acquisition

…………

5

…………………………………………

7

1.5 Modern Instrumentation Techniques

2.

…………………………

9

1.6 Project Description

…………………………………………

10

1.7 Summary

…………………………………………

11

PLANT AND PROCESS

[12-26]

Introduction

3.

2.1 Mathematical Modeling of Process Parameters …………………

13

2.2 Mathematical Simulation and Analysis

25

…………………

MECHANICAL MODEL Introduction

[27-32]

…………………………………………………

3.1 Industrial Prototype

…………………………………………

28 28

3.2 Liquid Level System

…………………………………………

29

3.3 Thermal System

…………………………………………

30

3.4 Servo Controlled Valve Mechanism

4.

………………………..

31

3.5 Overall Assembly

………………………………………..

32

3.6 Summary

………………………………………..

32

SENSOR & SIGNAL CONDITIONING Introduction

………………………………………………

34

4.1 Sensor’s Selection

………………………………………

34

4.2 Signal Conditioning

………………………………………

36

………………………………………………

46

4.6 Summary 5.

DIGITAL SCANNER Introduction

[47-57] ………………………………………………

48

5.1 Scanner in Industry

………………………………………

48

5.2 Required Features

………………………………………

48

5.3 Available Designing Techniques

………………………

49

5.4 Selected Design

………………………

50

5.5 Programming Flowchart ………………………………………

55

5.6 Possible Improvements

………………………………...

56

………………………………………………

57

5.7 Summary 6.

[33-46]

DAQ CARD CONFIGURATION Introduction

[58-69]

………………………………………………

6.1 Project Requirements

………………………………………

6.2 Indigenously Developed DAQ Card

………………………..

59 59 60

6.3 NI USB-6008 Multifunction DAQ Card

………………..

63

6.4 Getting Started Steps

………………………………………..

66

6.5 Device Recognition

………………………………………..

67

………………………………………………..

69

6.6 Summary 7.

HUMAN MACHINE INTERFACE

[70-81]

Introduction

………………………………………………..

71

7.1 LabVIEW

………………………………………………..

71

7.2 Data Acquisition Task

………………………………………..

74

7.3 Developed HMI ………………………………………………..

77

7.4 Block Diagram Programming

………………………………..

78

7.5 Summary

………………………………………………..

80

CONCLUSION

……………………………………………….

[81-84]

9. REFERENCES

……………………………………………….

[85-87]

10. APPENDICES

……………………………………………….

88

8.

10. A

NI USB-6008 DAQ User Guide

10. B

Controller Programming for Digital Scanner

10. C

Datasheets and Tables

10. D Project Manual

Multiplexed Industrial Data Acquisition System (MIDAS)

2

1.1 INSTRUMENTATION Instrumentation is about measurement and control. Instrumentation can refer either to the field in which instrument technicians and engineers work, or to the available methods of measurement and control and the instruments which facilitate this ‘[24]. Instruments are devices which are used in measuring attributes of physical systems. The variable measured can include practically any measurable variable related to the physical sciences. These variables commonly include: • Pressure • Flow • Temperature • Level • Density • Position • Radiation • Current • Voltage • Inductance • Capacitance • Frequency • Chemical composition • Chemical properties • Various physical properties Instruments can often be viewed in terms of a simple input-output device. For example, if we "input" some temperature into a thermocouple, it "outputs" some sort of signal. (This can later be translated into data) In the case of this thermocouple, it will "output" a signal in mill volts.

1.2 TRADITIONAL VERSUS VIRTUAL INSTRUMENTATION Stand-alone traditional instruments such as oscilloscopes and waveform generators are very powerful, expensive, and designed to perform one or more specific __________________________________________________________________ PCSIR - Institute of Industrial Electronics Engineering, IIEE ST-22/C, Block-6 Gulshan-e-Iqbal, Karachi – 75300

Multiplexed Industrial Data Acquisition System (MIDAS)

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tasks defined by the vendor. However, the user generally cannot extend or customize them. The knobs and buttons on the instrument, the built-in circuitry, and the functions available to the user, are all specific to the nature of the instrument. In addition, special technology and costly components must be developed to build these instruments, making them very expensive and slow to adapt ‘[30]. The primary difference between 'natural' instrumentation and virtual instrumentation is the software component of a virtual instrument. The software enables complex and expensive equipment to be replaced by simpler and less expensive hardware; for example analog to digital converter can act as a hardware complement of a virtual oscilloscope, a potentiostat enables frequency response acquisition and analysis. Virtual instruments are defined by the user while traditional instruments have fixed vendor-defined functionality.

Figure 1-1: Traditional instruments (left) and software based virtual instruments (right) largely share the same architectural components, but radically different philosophies [Courtesy NI website] Every virtual instrument consists of two parts – software and hardware. A virtual instrument typically has a sticker price comparable to and many times less than a similar traditional instrument for the current measurement task. However, the savings compound over time, because virtual instruments are much more flexible when changing measurement task. __________________________________________________________________ PCSIR - Institute of Industrial Electronics Engineering, IIEE ST-22/C, Block-6 Gulshan-e-Iqbal, Karachi – 75300

Multiplexed Industrial Data Acquisition System (MIDAS)

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By not using vendor-defined, prepackaged software and hardware, engineers and scientists get maximum user-defined flexibility. A traditional instrument provides them with all software and measurement circuitry packaged into a product with a finite list of fixed-functionality using the instrument front panel. A virtual instrument provides all the software and hardware needed to accomplish the measurement or control task. In addition, with a virtual instrument, engineers and scientists can customize the acquisition, analysis, storage, sharing, and presentation functionality using productive, powerful software. A virtual instrument consists of an industry-standard computer or workstation equipped with powerful application software, cost-effective hardware such as plug-in boards, and driver software, which together perform the functions of traditional instruments. Virtual instruments represent a fundamental shift from traditional hardware-centered instrumentation systems to software-centered systems that exploit the computing power, productivity, display, and connectivity capabilities of popular desktop computers and workstations. Virtual instruments are compatible with traditional instruments almost without exception. Virtual instrumentation software typically provides libraries for interfacing with common ordinary instrument buses such as GPIB, serial, or Ethernet. Engineers and scientists whose needs, applications, and requirements change very quickly, need flexibility to create their own solutions. You can adapt a virtual instrument to your particular needs without having to replace the entire device because of the application software installed on the PC and the wide range of available plug-in hardware.

__________________________________________________________________ PCSIR - Institute of Industrial Electronics Engineering, IIEE ST-22/C, Block-6 Gulshan-e-Iqbal, Karachi – 75300

Multiplexed Industrial Data Acquisition System (MIDAS)

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Virtual instrumentation is necessary because it delivers instrumentation with the rapid adaptability required for today’s concept, product, and process design,

development,

delivery.

Only

with

and virtual

instrumentation can engineers and scientists create the userdefined instruments required to keep

up

with

the

world’s

demands ‘[31].

Figure 1-2: Virtual instrumentation combines productive software, modular I/O, and scalable platforms. [Courtesy NI website]

1.3 VIRTUAL INSTRUMENTATION IN THE ENGINEERING PROCESS Virtual instruments provide significant advantages in every stage of the engineering process, from research and design to manufacturing test. [4]

1.3.1 RESEARCH AND DESIGN In research and design, engineers and scientists demand rapid development and prototyping capabilities. With virtual instruments, you can quickly develop a program, take measurements from an instrument to test a prototype, and analyze results, all in a fraction of the time required to build tests with traditional instruments. When you need flexibility, a scalable open platform is essential, from the desktop, to embedded systems, to distributed networks. The demanding requirements of research and development (R&D) applications require seamless software and hardware integration. Whether you need to interface stand-alone instruments using GPIB or directly acquire signals into the computer with a data acquisition board and signal conditioning hardware, VI makes integration simple. With virtual instruments, you also can automate a testing procedure, __________________________________________________________________ PCSIR - Institute of Industrial Electronics Engineering, IIEE ST-22/C, Block-6 Gulshan-e-Iqbal, Karachi – 75300

Multiplexed Industrial Data Acquisition System (MIDAS)

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eliminating the possibility of human error and ensuring the consistency of the results by not introducing unknown or unexpected variables.

1.3.2 DEVELOPMENT TEST AND VALIDATION With the flexibility and power of virtual instruments, you can easily build complex test procedures. For automated design verification testing, you can create test routines in LabVIEW and integrate software such as National Instruments TestStand, which offers powerful test management capabilities. One of the many advantages these tools offer across the organization is code reuse. You develop code in the design process, and then plug these same programs into functional tools for validation, test, or manufacturing.

1.3.3 MANUFACTURING TEST Decreasing test time and simplifying development of test procedures are primary goals in manufacturing test. Virtual instruments based on LabVIEW combined with powerful test management software such as TestStand deliver high performance to meet those needs. These tools meet rigorous throughput requirements with a high-speed, multithreaded engine for running multiple test sequences in parallel. TestStand easily manages test sequencing, execution, and reporting based on routines written in LabVIEW. TestStand integrates the creation of test code in LabVIEW. TestStand also can reuse code created in R&D or design and validation. If you have manufacturing test applications, you can take full advantage of the work already done in the product life cycle.

1.3.4 MANUFACTURING Manufacturing applications require software to be reliable, high in performance, and interoperable. Virtual instruments based on LabVIEW offer all these advantages, by integrating features such as alarm management, historical data trending, security, networking, industrial I/O, and enterprise connectivity. With this __________________________________________________________________ PCSIR - Institute of Industrial Electronics Engineering, IIEE ST-22/C, Block-6 Gulshan-e-Iqbal, Karachi – 75300

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functionality, you can easily connect to many types of industrial devices such as PLCs, industrial networks, distributed I/O, and plug-in data acquisition boards. By sharing code across the enterprise, manufacturing can use the same LabVIEW applications developed in R&D or validation, and integrate seamlessly with manufacturing test processes.

Figure 1-3: LabVIEW is a leader in application software used in PC-based data acquisition and instrument control. [Survey of Design News and R&D Magazine, QI 2004]. Figure 1-3 shows the increasing strength of NI LabVIEW based virtual instrumentation in the engineering processes of R&D and industry over other available software packages. The increasing advancement and functionality of NI LabVIEW will soon replace the traditional and other software based virtual instrumentation.

1.4 DATA ACQUISITION Data acquisition is the processing of multiple electrical or electronic inputs from devices such as sensors, timers, relays, and solid-state circuits for the purpose of monitoring, analyzing and/or controlling systems and processes. Instruments or systems are fully packaged with input and output, user interface, communications capability, etc. They may include integral sensors. Input modules are devices (module or card) configured to accept input of sensors, timers, switches, amplifiers, transistors, etc. for use in the data acquisition __________________________________________________________________ PCSIR - Institute of Industrial Electronics Engineering, IIEE ST-22/C, Block-6 Gulshan-e-Iqbal, Karachi – 75300

Multiplexed Industrial Data Acquisition System (MIDAS)

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system. Output modules are devices with specific functionality for output of amplified, conditioned, or digitized signal. I/O modules have both input and output functionality. Digital or discrete I/O includes on-off signals used in communication, user interface, or control. A general data PC based data acquisition system is shown in figure 1.4:

Figure 1.4: A PC based data acquisition [Courtesy National Instrument Website]

A typical data acquisition system consists of: ‰ Transducers ‰ Signal Conditioning ‰ Plug-in DAQ device ‰ Driver ‰ Software Acquired data is displayed, analyzed, and stored on a computer, either using vendor supplied software, or custom displays and control can be developed using various general purpose programming languages such as BASIC, C, Fortran, Java, Lisp, Pascal. Specialized programming languages used for data acquisition include, EPICS used to build large scale data acquisition systems, LabVIEW, which offers a graphical programming environment optimized for data acquisition and MATLAB provides a programming language but also built-in graphical tools and libraries for data acquisition and analysis.

__________________________________________________________________ PCSIR - Institute of Industrial Electronics Engineering, IIEE ST-22/C, Block-6 Gulshan-e-Iqbal, Karachi – 75300

Multiplexed Industrial Data Acquisition System (MIDAS)

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1.5 MODERN INSTRUMENTATION TECHNIQUES The required task can be practically implemented by several techniques depending upon complexity of the task. We studied three techniques given below and choose the best one on the bases of available technology, degree level and industrial requirement.

1.5.1 WIRELESS SOLUTION One method to achieve task was to use wireless communication technique. By using this technique we have to make individual transmitter for each transducer and one receiver for all transmitters if only monitoring is required. Signal of each transducer is converted into electromagnetic wave and is transmitted through radio antenna. Receiver is tuned over that particular quantity’s frequency. If we are using only one receiver then we has to auto scan it for all quantities frequency because receiver can catch only one signal at a time. The choice of receiver’s quantity depends on the response of physical quantities. If response is very fast changing as in case of mechanical vibration then we have to use single receiver for that particular quantity. But in case of slow variant quantity we can use single receiver for more than one quantity. We did not select this technique because this technique was using wireless communication which is avoided in industry. One signal can interfere with other signals in air at same frequencies which may be harmful.

1.5.2 DATA NETWORKING Second method to achieve this task was to use any one networking topology. By using networking topology we can insert as many transducers as we want and now a days it is standard which is being used in industry. In this technique each transducer is server on the selected topology bus while our host computer is client. Servers provide information whenever client request it. So we program the client request so that it demands new server information after selected time and go ahead to get information from next server. When all required servers information is completed it again repeats cycle and updates all servers’ information and shows on the __________________________________________________________________ PCSIR - Institute of Industrial Electronics Engineering, IIEE ST-22/C, Block-6 Gulshan-e-Iqbal, Karachi – 75300

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display panel. It is the cheapest way to achieve this task. But in this designing technique we have to make all transducer as server so that they can work as servers on topology bus. This technique was best but we still did not use this technique because we have to make each transducer a server and have to log it on selected topology bus. This technique required complex knowledge of networking communication while our primary concern was to design data acquisition card but not to implement networking topologies.

1.5.3 DIRECT CABLE SYSTEMS A third and last technique was to pick the signal directly from the physical system through cables without networking and after suitable signal conditioning these signals are fed to DAQ card. This method is mostly adopted by the industry due to its safe and secure nature. It removes all the dangers of signal interruption. It also provides the simple design to implement. We have selected this one as it does not involve signal transmission complexities as was in above given techniques and one can work upon his concern problem that is DAQ card and it’s HMI. In all technique the received signals are provided to the DAQ card. We take our signal’s quantity and direct insert into DAQ card. We employed here three analog inputs of DAQ card which can be multiplexed up to eight inputs.

1.6 PROJECT DESCRIPTION Monitoring of physical parameters in different industrial fields with accuracy always remains a problem. Different techniques were developed to make monitoring as friendly as possible so that operators and engineers can control parameters easily. HMI or GUI gives the user friendly controlling and monitoring interface of actuators and transducer to operators. These days all industries are going to revolutionizes with advancement in technology especially in the field of instrumentation. In any process industry control room is the mind of the industry which takes production related decision and which also monitor all the physical parameters. These parameters are __________________________________________________________________ PCSIR - Institute of Industrial Electronics Engineering, IIEE ST-22/C, Block-6 Gulshan-e-Iqbal, Karachi – 75300

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displayed on monitoring panels which shows the GUI for the DAQ cards working behind the monitoring panel. The proceeding project can be divided into two main parts which are described as follows:

1.6.1 HARDWARE The hardware consists of DAQ card and transducer’s signal conditioning cards. We have used USB-6008 national instrument DAQ card for our instrumentation system. The signal conditioning is done to make transducer’s signals compatible with DAQ card.

1.6.2 SOFTWARE We have used LABVIEW software for designing our graphical user interface. All quantities are displayed on pc screen through knobs, dial and digital indicator. Due to increasing popularity of LABVIEW in virtual instrumentation, we decided to use this software.

1.7 SUMMARY We started this chapter with the introduction of instrumentation system and then differentiated the traditional and virtual instrumentation. Virtual instrumentation in process engineering and data acquisition is also discussed here in detail. As we saw in this chapter that there is a number of different techniques to solve the problem of industrial data acquisition. We discussed three most important techniques here. In the end we discussed project objectives dividing it into two sections that are hardware and software.

__________________________________________________________________ PCSIR - Institute of Industrial Electronics Engineering, IIEE ST-22/C, Block-6 Gulshan-e-Iqbal, Karachi – 75300

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INTRODUCTION This chapter is concerned with the analysis and simulation of our system by developing its mathematical model of level and thermal system and the speed of servo mechanism. For level measurement a pot meter is implemented which will provide the linear output voltage proportional to the level height. In process temperature, the temperature is measured by thermocouple up to 750C.

2.1 MATHEMATICAL MODELLING OF PROCESS PARAMETERS Mathematical modeling of different plants of our project is given one by one as follow.

2.1.2 THERMAL SYSTEM In this thermal system the temperature of the furnace is monitored up to 600OC using thermocouples. The furnace is provided energy through electrical supply as shown in figure 2.1:

Figure-2.1: A thermal system block diagram Thermocouples are linear over long range and suitable in the rigged environment also inexpensive and versatile devices for measuring temperature. Before going into the mathematics of thermocouple one should understand see beck effect [22]. “Electrically conductive materials exhibit three types of thermoelectric phenomena: __________________________________________________________________ PCSIR - Institute of Industrial Electronics Engineering, IIEE ST-22/C, Block-6 Gulshan-e-Iqbal, Karachi – 75300

14

Multiplexed Industrial Data Acquisition System (MIDAS)

The See beck effect, the Thompson effect, and the pettier effect. The See beck Effect is manifest as a voltage potential that occurs when there is a temperature Gradient along the length of a conductor. This temperature-induced electrical Potential is called an electromotive force and abbreviated as EMF.” Figure 2.1: represents a conceptual experiment that exhibits the See beck effect. The two ends of a conducting wire are held at two different temperatures T1and T2. For clarity, assume that T2 > T1, although with appropriate changes of sign, the development that follows is also applicable to the case where T2 < T1.If the probes of an ideal voltmeter could be connected to the two ends of the Wire without disturbing the temperature or voltage potential of the wire, the Voltmeter would indicate a voltage difference on the order of 10−5 volts per degree Celsius of temperature difference. The relationship between the EMF and the temperature difference can be represented as

E 12 = σ (T 1 − T 2) Where σ is the average See beck coefficient for the wire material.

(2.1)

Figure-2.2 See Back Effect In general, the See beck coefficient is a function of temperature. To develop a more precise and versatile relationship than Equation (2.1), consider an experiment Where T1 is fixed, and T2 is varied. For practical thermocouple materials the relationship between E and T is continuous. Hence, for sufficiently small Change

σ T2 in T2, the EMF indicated by the voltmeter will change by a corresponding Small __________________________________________________________________ PCSIR - Institute of Industrial Electronics Engineering, IIEE ST-22/C, Block-6 Gulshan-e-Iqbal, Karachi – 75300

15

Multiplexed Industrial Data Acquisition System (MIDAS)

amount σ E12. Since σ T2 and σ E12 are small, it is reasonable to linearize the EMF response as

E12 + ∆E12 = σ (T 2 − T 1) + σ (T 2)∆T 1

(2.2)

Where ó (T2) is the value of the See beck coefficient at T2. The change in EMF only depends on the value of the See beck coefficient at T2 because T1 is held fixed. Subtract Equation (2.1) from Equation (2.2) to get

∆E 12 = σ (T 2) ∆T 2 This can be rearranged as

σ (T 2) =

∆E12 ∆T 2

(2.3)

(2.4)

If ó is an intrinsic property of the material, then the preceding equation must hold for any temperature. Replacing all references to T2 with an arbitrary temperature T, and taking the limit as the temperature perturbation goes to zero, gives

σ (T ) =

∆T lim 0

dE dT

(2.5)

Using the Fundamental Theorem of Calculus, the limit becomes a derivative. The result is the general definition of the Seebeck Coefficient

σ (T )

=

∆T

lim 0

dE dT

(2.6)

Equation (2.6) contains all the theoretical information necessary to analyze thermocouple circuits. Practical exploitation of the Seebeck effect to measure temperature requires a combination of two wires with dissimilar Seebeck coefficients. Figure 2.2: represents such a basic thermocouple. The two wires of the thermocouple are joined at one end called the junction, which is represented by the solid dot on the right side of Figure 2.2.The junction is in thermal equilibrium with a local environment at temperature Tj . The other ends of the thermocouple wires are __________________________________________________________________ PCSIR - Institute of Industrial Electronics Engineering, IIEE ST-22/C, Block-6 Gulshan-e-Iqbal, Karachi – 75300

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attached to the terminals of a voltmeter. The voltmeter terminals are both in thermal equilibrium with a local environment at temperature Tt.

Figure-2.3: A simple thermocouple Equation (2.6) is applied to the thermocouple circuit in Figure 2 by writing

dE = σ (T ) dT

(2.7) Thus, the EMF generated in material A between the junction at Tt and the junction at Tj is Tj

EA, tj = ∫ σ A(T )dT

(2.8)

Tt

Applying Equation (2.8) to consecutive segments of the circuit gives Tj

Tt

Tt

Tj

E AB = ∫ σ AdT + ∫ σ BdT

(2.9)

Where óA is the absolute Seebeck coefficient of material A and óB is the absolute Seebeck coefficient of material B. The order of integration is specified by moving continuously around the loop: from the terminal to the junction, and back to the terminal. Notice that the value of EAB in Equation (2.9) is due to integrals along the length of the thermocouple elements. This leads to the following essential and often misunderstood fact of thermocouple thermometry: The EMF generated by the See beck effect is due to the Temperature gradient along the wire. The EMF is not generated At the junction between two dissimilar wires. __________________________________________________________________ PCSIR - Institute of Industrial Electronics Engineering, IIEE ST-22/C, Block-6 Gulshan-e-Iqbal, Karachi – 75300

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The EMF of the thermocouple exists because there is a temperature difference between the junction at Tj and the open circuit measuring terminals at Tt. Switching the order of the limits for the second integral in Equation (2.9) allows the following manipulation Tj

Tj

Tj

Tt

Tt

Tt

EAB = ∫ σ AdT − ∫ σ BdT = ∫ (σ A −σ B ) dT

(2.10)

Now define the Seebeck coefficient for the material pair AB as

σ AB = (σ A σ B ) −

(2.11)

Substituting the definition of óAB into Equation (10) gives Tj

EAB = ∫ σ ABdT

(2.12)

Tt

Equation (2.12) is the fundamental equation for the analysis of thermocouple circuits. It is not yet in the form of a computational formula for data reduction. Before a data reduction formula can be developed, however, the role of the reference junction needs to be clarified given bellow, Equation (2.12) shows how the EMF generated by a thermocouple depends on the temperature difference between the Tj and Tt. All thermocouple circuits measure one temperature relative to another. The only way to obtain the absolute1 temperature of a junction is to arrange the thermocouple circuit so that it measures Tj relative to an independently known temperature. The known temperature is referred to as the reference temperature Tr. A second thermocouple junction, called the reference junction, is located in an environment at Tr.

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Figure-2.4: Physical circuit for thermocouple

Figure-2.5: Conceptual T(x) plot of thermocouple Figure 2.3 shows a thermocouple circuit with a reference junction at temperature Tr. At the reference junction, copper extension wires connect the voltmeter to the legs of the thermocouple. The thermocouple wires are labeled P for positive and N for negative. Beginning with the terminal block at temperature Tt, there are five junctions around the circuit. Using x as a position indicator, the five labeled junctions are numbered in order of increasing x. To find the EMF produced by the thermocouple circuit in Figure 2.4, apply Equation (2.8) to each segment of wire in the circuit Tr

Tj

Tr

Tt

Tt

Tr

Tj

Tr

E 15 = ∫ σ CdT + ∫ σ PdT + ∫ σ NdT + ∫ σ CdT

(2.13)

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Where óC is the absolute See beck coefficient of copper, óP is the absolute See beck coefficient of the material in the positive leg, and óN is the absolute See beck coefficient of the material in the negative leg. Reversing the limits of integration for the first term in Equation (2.13) gives

Tr

∫σ

Tt

Tt

C

dT = − ∫ σ CdT

(2.14)

Tr

Therefore, the first and last terms in Equation (2.13) cancel. Furthermore, reversing the limits of integration in the third term in Equation (2.13) and simplifying yields Tj

E 15 =

∫σ

PN

dT

(2.15)

Tr

Where óPN = óP − óN

The result in Equation (2.15) can be interpreted graphically with the lower half of Figure 2.4. The EMF across the copper segments 1-2 and 4-5 cancel because the EMF on these segments is of equal magnitude and opposite sign. Think of going down in potential from 1 to 2, and up in potential from 4 to 5. The EMF across segments 2-3 and 3-4 does not cancel, however, because the absolute Seebeck coefficients for these two segments are not equal. Indeed, a thermocouple is only possible when two dissimilar wires are joined so that óPN = óP − óN

The circuit in Figure 2.4 provides a practical means for measuring temperature Tj relative to temperature Tr. To use this circuit an independent method of measuring Tr is required, along with the value of óPN. The calibration tables and equations use Equation (2.15) with a reference temperature of 0ο C , which is easily obtainable with a mixture of ice and water. The integral in Equation (2.15) is a formal statement of the relationship between EMF on temperature. To develop a calibration for a particular thermocouple type, the EMF is measured as Tj is varied and Tr is held fixed at 0ο C .

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The result of the calibration is a table of EMF versus T values. The integral is never directly evaluated. Instead a polynomial curve fit to the calibration data gives

E 0 j = F (Tj ) = b 0 + b1Tj + b 2Tj 2 + … + bnTj

(2.16)

In terms of the formalism of the preceding sections, Tj

Eoj = ∫ σ PNdT

(2.17)

0

From the same calibration data a curve fit of the form

Tj = G ( Eoj ) = c 0 + c1Eoj + … + cmE 0 j m

(2.18)

is also obtained. The F(Tj) and G(E0j) symbols provide convenient shorthand notation for the two calibration polynomials. Equation (2.18) is directly useful for temperature measurements with thermocouples. For the circuit in Figure 2, with Tr = 0, Equation (2.18) allows a measured EMF to be converted to a temperature. Figure 2.4 depicts a useful thermocouple circuit. The most straightforward implementation of this circuit is to place the reference junctions (block labeled Tr) in an ice bath. The resulting circuit is sketched in Figure 2.5. The two junctions can share the same ice bath if they are electrically insulated from each other

Figure-2.6: Cold junction compensation For the thermocouple circuit in Figure 2.5, the standard calibration equations are used directly. Applying Equation (2.12) to each segment of wire in the circuit gives __________________________________________________________________ PCSIR - Institute of Industrial Electronics Engineering, IIEE ST-22/C, Block-6 Gulshan-e-Iqbal, Karachi – 75300

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Tb

Tj

Tr

Tb

Tt

Tt

Tb

Tj

Tr

Tb

E16 = ∫ σ CdT + ∫ σ PdT + ∫ σ NdT + ∫ σ pdT + ∫ σ CdT

(2.19)

The first and last integrals cancel, (Cf. Equation (2.14).) Rearranging the remaining terms gives Tb

Tj

Tr

Tr

Tb

Tj

E16 = ∫ σ PdT + + ∫ σ pdT + ∫ σ NdT Tj

Tj

Tr

Tr

E16 = ∫ σ PdT − ∫ σ NdT (2.20)

Tj

E16 = ∫ σ PNdT Tr

ο

Since Tr = 0 C (the standard reference temperature), Equations (2.17) and (2.18) may

be used directly for the thermocouple circuit in Figure 2.5. The equation (2.16) is the voltage produced by thermocouple when reference junction is at 0ο C Now neglecting the square and higher order terms in equation (2.16) gives direct linear relationship between junction temperature & produced emf.

E 0 j = F (Tj ) = b 0 + b1Tj

(2.21)

Note that the nonlinearity increase with increase in temperature due to variation in material coefficient.

2.1.2 SERVO MOTOR

Figure-2.7: A general block diagram for position control The general transfer function of the motor [18] __________________________________________________________________ PCSIR - Institute of Industrial Electronics Engineering, IIEE ST-22/C, Block-6 Gulshan-e-Iqbal, Karachi – 75300

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G ( s ) = ( s (1K+τ s ) ) Calculating

τ

(2.22)

:

First we coupled our motor without gears with another motor and applied voltage on it and measured the output voltages (generator action) as well as the RPMs of the external motor. The following readings were obtained Table-2.1:Reading for generator action Applied Voltages Generated Voltages (v) (v)

7 8.5 10 12

2.7 3.6 4.8 5.15

Table-2.2: Applied and generated voltages. rad/sec

Generated voltage

70 90 100 115

2.7 3.6 4.8 5.15

The corresponding graphs are shown on the next page in figure 2.8 and 2.9. Calculating the values of the feedback gain from the graph is taken as

∆rad / sec = 20 ∆v = 0.7v

Since

Kb =

∆rad / sec ∆v

(2.23)

Kb = 28.57 rad / sec/ v The forward gain will be

K=

1 Kb

(2.24)

K = 0.035v / rad / sec __________________________________________________________________ PCSIR - Institute of Industrial Electronics Engineering, IIEE ST-22/C, Block-6 Gulshan-e-Iqbal, Karachi – 75300

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Figure-2.8: Graph between generated voltage and applied voltage.

Figure-2.9: Graph between generated voltage and applied RPM

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The τ is the sum of electrical ( τ e ) plus mechanical ( τ m )

τ = τ e +τ m But Therefore neglecting

τe

(2.25)

τ m >> τ e τ =τm

Where

τ = τ m = (RKb. Jo)

2

(2.26)

Now calculating motor’s parameters

Jo =

K IFL − INL

Jo =

(2.27)

0.035 210 −170

Jo = 0.875 v / rad / sec/ mA

τ = (RKb. Jo)

(2.28)

2

Where

R = 70Ω τ = 0.075sec

So the transfer function of the motor became

G( s) = ( s (1+0.035 0.075 s ) )

(2.29)

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2.2

MATHEMATICAL SIMULATION & ANALYSIS The mathematical simulation results for level, temperature and position are

shown and analyzed.

2.2.1 THERMOCOUPLE Taking data from the standard thermocouple reference table, following graph has been drawn for our required range [10]. 60

Thermoelectric Voltage (mV)

50

40

30

20

10

0

0

100

200

300

400 500 600 Temprature (C)

700

800

900

1000

Figure-2.10: Graph for J-Type Thermocouple The graph shows that thermocouple offers very high mark of linearity over a long temperature range which makes it very applicable in industrial measurement for high temperatures and in the rugged environment as well.

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2.2.2 SERVO MOTOR The transfer function of the motor was came out to be

G( s) = ( s (1+0.035 0.075 s ) )

(2.30)

Applying unit impulse, the open loop response came out as

Impulse Response 0.035

0.03

Amplitude

0.025

0.02

0.015

0.01

0.005

0

0

20

40

60

80

100

120

140

160

Time (sec)

Figure-2.11: Open loop impulse response

The graph shows that system is unstable in open loop as it is not being get settled by achieving settle down back. The system can be made stable in close loop configuration or applying suitable compensator like P, PI, PD, PID controllers.

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INTRODUCTION This chapter concentrates on the description of whole mechanical assembly of our project. As we know that it is always remained a problem to measure the physical quantity accurately and to solve this problem different techniques are used to develop the mechanical models as friendly as possible so that operators and engineers can measure and control the required parameters. Since after the selection of suitable sensors and mathematical modeling for their parameters it was necessary to implement the design by developing the precise mechanical model for the measurement of selected parameters with accuracy. In this project three individual models are developed that is level system, thermal system and servo controlled valve mechanism which then finally assembled.

3.1 INDUSTRIAL PROTOTYPE A working model created to demonstrate fundamental aspects of industrial measurements without creating a detailed program. Adding details and content incrementally to advancing stages of prototypes is one process for creating successful applications. In this project a sample prototype of industrial measurements is fabricated in advance of production to allow monitoring, controlling, demonstration, evaluation, or testing of the physical parameters, which is a full-scale working model of an original industrial measurements or an updated version of existing industries.

The project mechanical model is developed as accurately as possible to meet the industrial standard prototype. It is not only developed for the project purpose but can also be exercised in institute practical work of students for instrumentation and control subjects. It will help in understanding the proper placement of different sensors for different plants.

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3.2 LIQUID LEVEL SYSTEM As level of liquid was first parameter to measure in our project so in order to implement the proposal we have made a tank with the width ,height and length all equal to one foot. According to the requirement we have set two limits that is upper and lower limit. Upper limit was marked up to 260mm height and lower limit up to 5mm.Since we have used water column based current transmitter to measure the level which gives the output current on basis of pressure difference, so we attached two nozzles that is one at ground level of tank and other at upper limit. When current transmitter is connected to these two nozzles through pipes, a pressure difference is created which fulfils the transmitter’s requirement. The inlet of the tank is through the motor pump from the reservoir while the outlet is attached with servo controlled valve mechanism so that the outlet flow is controlled at ground level of tank as shown in figure 3-1. The tank is placed at a certain height of about 10 inches

from

the

base

board in order to fulfill the proper

functioning

of

current transmitter so that it can take the proper pressure for its lower limit (zero limits).

Figure 3-1: Mechanical model for liquid level system with inlet pump motor.

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3.3 THERMAL SYSTEM Since we are measuring a high temperature range up to 600 oC using Jtype thermocouple sensor, so it was really very difficult to develop such high temperature in the lab. To serve the purpose we have taken a solder iron of 500 watts which could generate highest temperature of 1200 oC which was fulfilling our requirement and best suited for the model as it reserves a very narrow space and could easily be isolated for safety purpose. This solder iron is used as furnace which is heated by electric utility of 220 volts AC. A voltage regulator is also used to control the temperature of the furnace. For protection from such high temperature we surrounded the furnace with thick wooden block with thin metallic sheets at inner side of wooden block so that maximum temperature may absorbed by the sheets and block remain safe as shown in figure 3-2.

Figure 3-2: Electric furnace surrounded by wooden block for safety and protection attached with the temperature controller. The controller is based upon SCR pulse firing technique

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3.4 SERVO CONTROLLED VALVE MECHANISM The third parameter to be measured in the project was position of servo controlled valve to control the outlet flow of the liquid tank as in addition to measurement we also have introduced its controlling option in the project. For position measurement and control we have developed the mechanism of a valve and attached it with the outlet to liquid tank. This valve is coupled both with the geared dc motor and the feedback pot meter in such a way that opening and closing of valve changes the resistance. The valve takes five turns of rotation to completely open or close; therefore the ten turn pot meter is used as a sensor, so when the whole valve is fully opened or closed it utilizes its five turns which falls in the midrange of feedback sensor. The servo controlled valve mechanism is shown in figure 3-3.

Figure 3-3: Servo controlled valve mechanism to control the outlet flow of liquid tank

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3.5 OVERALL MECHANICAL ASSEMBLY As the mechanical model for each of three parameters being measured is developed, so it was necessary to assemble them together. In order to serve the purpose we have taken a wooden block and all individual models have assembled on it using solid screws. Pictorial view of the whole mechanical assembly of our project is below:

Figure-3.4: Overall mechanical assembly

3.6 SUMMARY In this chapter we discussed the importance of mechanical assembly from the industrial point of view and introduced the industrial prototype development which follows the fabrication of individual mechanical models for the accurate measurement of the selected physical parameters which are level system, thermal system and servo controlled valve mechanism. To satisfy the rules of simplicity finally all these models are assembled on a single wooden block. __________________________________________________________________ PCSIR - Institute of Industrial Electronics Engineering, IIEE ST-22/C, Block-6 Gulshan-e-Iqbal, Karachi – 75300

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INTRODUCTION In general for measuring the effect of any physical quantity like temperature, pressure, level etc we require some kind of device called a sensor. Sensors are used in everyday objects such as touch-sensitive elevator buttons and lamps which dim or brighten by touching the base. There are also innumerable applications for sensors of which most people are never aware. Applications include automobiles, machines, aerospace, medicine, industry, and robotics. Signal conditioning is to process the form or mode of a signal, taken from sensor usually but not always, so as to make it intelligible to or compatible with a given device, such as a data acquisition card, dial indicator, recorders etc.In our project we signal conditioned all quantities to give 0 to 5V so as they could be interfaced with DAQ card and digital scanner.

4.1 SENSOR’S SELECTION For measuring one type of physical quantity a lot of sensors are available in market so selection of a proper sensor for a particular quantity becoming a specialized field. As we are measuring three most important and common industrial parameters (liquid level, temperature and position) we divide their selection in proceeding sections.

4.1.1 SENSOR FOR LIQUID LEVEL SYSTEM During selection of liquid level sensor there were several options we had. First of all we thought about potentiometer based liquid level sensor which is most common method of measuring liquid level at this stage. As we have told that we were going to make this project an industrial prototype so we required some industrial sensor. We decided to make the potentiometer base method as stand by and started to search some suitable Sensor from industries. Variety of sensors was available in industry working on different principles. __________________________________________________________________ PCSIR - Institute of Industrial Electronics Engineering, IIEE ST-22/C, Block-6 Gulshan-e-Iqbal, Karachi – 75300

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By definition all transmitter gives current output in contrast to the transducers which give voltage output. The use of transmitter (current output) is exponentially increasing by replacing the transducers (voltage output). We got level transmitter which was actually a difference pressure water column level transmitter. It holds the following main advantages: •

It could measure up to 600 millimeter level which falls within our required range.

•

It could be used both in 2-wire and 3-wire configuration

•

It could be calibrate both for 0 to 20mA and 4 to 20mA.

4.1.2 SENSOR FOR THERMAL SYSTEM To meet the needs of an industrial prototype we decided to measure temperature above 500oC. LM35 is common sensor for measuring temperature but it is used only for non-contact measurements like ambient temperature. We rejected the LM35 due to the reason that first it is a non-contact and low temperature purposes second it gives about 5oC error at room temperature. So different sensors were available for temperature measurement but we selected the thermocouple due to following reasons: •

Capable of being used to directly measure temperatures up to 2600oC.

•

The thermocouple junction may be grounded and brought into direct contact with the material being measured.

•

Thermocouples allow measurement of temperatures higher than that possible with resistance devices (RTDs) like the platinum resistance thermometer. Their operating range is far wider: compare -200 to 650°C for platinum probes with -200 to more than 2000 °C with refractory thermocouples.

•

Thermocouples are inexpensive, rigid and easy to construct as compare to any other temperature sensor.

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4.1.3 SENSOR FOR CONTROLLED VALVE MECHANISM Besides measuring the position of valve we are controlling the position of liquid flow control valve as an application of position control. So for measuring the valve position we required a sensor which generate electrical signal in response to the varying position of valve. For this purpose we decided to use potentiometer as feedback sensor. The total number of turns involved in opening and closing of valve were five so we arranged a ten turn potentiometer as feedback sensor. Encoder could also be used as feedback sensor but it does not give continuous output and also an expensive option so we rejected this option.

4.2 SIGNAL CONDITIONING We configure DAQ card for 0V to 5V range and developed soft display for this range similarly we also designed digital scanner for this range. So we wanted to make signal compatible with this range. For this purpose we had to signal conditioned our all quantities.

4.2.1 SIGNAL CONDITIONING FOR LEVEL TRANSMITTER

As we have already discussed that for level measurement we used industrial level transmitter. It was a current output transmitter and we had to convert this current into voltage. We used level transmitter in 3-wire configuration with 0 to 20mA output. Before converting current into voltage we had to calibrate it first as follow so we divide signal conditioning of level transmitter into two parts first calibration and second signal conditioning. The detailed about calibration of level transmitter is given in project manual for user in Appendix 10.D. Different reading obtained during calibration are given in Table- 4.1 and its corresponding graph is given in Figure-4.1

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Tabel-4.1: Level Transmitter output table during Calibration S# 1 2 3 4 5 6 7 8 9 10 11

Tank Height (mm) 0 27 54 81 108 135 162 189 216 243 270

Transmitter output (mA) 0.2 1.99 4.01 6.2 7.98 10.07 12.1 13.99 16.3 17.89 19.79

Figure-4.1: Graph between transmitter output and height of level

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When transmitter was calibrated for full range we converted this current to voltage for further processing. We placed a 250ohms burden load at transmitter’s output which as to get voltage and then used an operational amplifier in current-to-voltage configuration as shown in Figure-4.2. The detailed circuit of this block diagram is shown next in Figure-4.3.

Figure-4.2: Block Diagram of Level Transmitter Signal Conditioning

Figure-4.3: Circuit Diagram of Level Transmitter Signal Conditioner

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4.2.2 SIGNAL CONDITIONING FOR THERMOCOUPLE The toughest job in our sensor’s signal conditioning portion was thermocouple’s signal conditioning. The main problem in thermocouple signal conditioning is its cold junction compensation and its nonlinearity at higher temperature. To overcome these problems we used Analog Device’s an expensive industrial signal conditioner AD594AQ which have built-in cold junction compensation and nonlinearity adjustment. However there were small non-linearties still in AD594’s output so we used positive feedback to remove this non-linearity. The detail of signal conditioner’s adjustment with thermocouple voltage is given below.

Before going into detail it is necessary to remember that AD594AQ is factory calibrated at 10mV/

o

C. For measuring the atmosphere

temperature and furnace temperature we used RTD (pt-100) as reference sensor. RTD’s measured resistance at different temperature and its corresponding table is shown in Table-4.2 and respective graph in Figure-4.4. Table-4.2: RTD's measured values

# 1. 2. 3. 4.

Temperature o C 0 32 212 410

Resistance (ohms) 100 113 180 250

Figure-4.4: Graph between temperature and RTD Output

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Now we took thermocouple wires and connected to IC’s input and check IC’s output voltage. It was showing that voltages which were when converted to temperature was giving room temperature at that time is 32 oC. Same times we measured RTD resistance that was also showing the same room temperature. Now this time we put thermocouple in furnace and adjust the temperature at 400 oC with the help of RTD as reference temperature sensor. Again we measured output voltage of IC it was showing the same temperature that is 400 oC. Different readings obtained during AD594’s calibration and their corresponding graph is shown in Table4.3 and Figure-4.5. Table-4.3: AD594 output voltage with respect to temperature. S.No

Temperature o

AD594 output voltage

C

V

1.

0

0

2.

32

0.32

3.

212

2.13

4.

410

4.12

Figure-4.5: Graph between AD594 output voltage with respect to temperature

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The detail of the used reference temperature sensor, selected signal conditioner and thermocouple output with corresponding tables and graphs was given in above discussion. Now we can draw a simple block diagram of the thermocouple signal conditioning as shown in Figure-4.6. Corresponding detailed circuit diagram of the block diagram is given in Figure-4.7.

Figure-4.6: Block Diagram of Thermocouple Signal Conditioning Output

The LED shown in Circuit diagram of thermocouple signal conditioner is for fault indication. The only possible fault in thermocouple is its opening from hot junction because of excessive heat. Whenever thermocouple becomes open or input supply exceeds its limit, this LED will blink.

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Figure-4.7: Circuit Diagram of Thermocouple Signal Conditioner

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4.2.3 SIGNAL CONDITIONING FOR FEEDBACK MECHNUSM We have already discussed that we are not only measuring but also controlling the servo valve using potentiometer as feedback sensor for measurement and PI controller for position control. The block diagram of the controlling and measuring system is given as follow in Figure-4.8.

Figure-4.8: Block Diagram of PI Controller for Controlled Valve We used voltage source for excitation of potentiometer which was giving our required linearity. However we could use current source which was a difficult option but current source is always used where a high degree of linearity is required. After excitation of potentiometer following different readings were taken during calibration shown in Table-4.4:

Where as the graph taken from above readings are shown in figure-4.9. The graph shows that sensor’s output is quite linear and does not require linear zing it __________________________________________________________________ PCSIR - Institute of Industrial Electronics Engineering, IIEE ST-22/C, Block-6 Gulshan-e-Iqbal, Karachi – 75300

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further. It just requires further to buffer the signal before giving it to the data acquisition card in order to avoid loading effects.

As shown in Table-4.4: that the sensor’s minimum output was 0.36V and maximum output was 2.8V but we wanted minimum signal 0V and maximum, when valve is fully closed, 5V. So to get our required limits we have to signal conditioned this sensor by inserting an operational amplifiers based network which in turn gave us our required limits. We designed PI controller for servo valve for controlling the flow of liquid. The detailed circuit diagram of PI controller is given in Figure-4.10.

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REFERENCE 3

2

10k

2

1

+5 V

5K

1

3

5K +

-

-

1k

6

LM741

+

2

3

-

2

3 OP-07

+

1k

1k

1k

2

3 OP-07

6 6

1k

1k

1k

1k 1k

1 -

250k

+

-

1

2

3 LM741

5k

+

2

3 LM741

2

2

3

6

6 3

220 Ohm

Title

Size A

Date:

2

2

+Vss

BD243

3

1

BD244

1

3

-Vee 1k

Sheet

1 3 2

1k

+5 V

1

1 Rev

0V TO 5V

of

(To Measuring system)

1

Motorised Valve controlling Ckt.

Saturday , September 22, 2007

Document Number

2

Servo Control Valve

Figure-4.10: Circuit Diagram of proportional controller for the servo controlled valve.

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4.3 SUMMARY This chapter was consisting of two main parts. One was the selection of different sensors which were suitable for our required processes and second was their signal conditioning in which we made sensors output compatible with our required output. In sensor’s selection we selected differential pressure level transmitter for our liquid level system and we also discussed how this transmitter was best suitable for our requirement. For temperature measurement we choose thermocouple j-type and for feedback sensor in controlling the position of valve we selected potentiometer. In signal conditioning of all sensors we made all output signals compatible with our required range that was 0V (for minimum) and 5V (for maximum) using different techniques discussed in this chapter in detail.

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INTRODUCTION “A system that reports the value of a physical quantity in numerical form one by one is called a digital scanner.” When a measurement is made (such as in our project thermocouple, level transmitter & a servo controlled valve) a numerical quantity is determined from a physical quantity, at a specific time and location. It is important to define exactly what is being measured: is it all three components of a vector, one component of a vector, a magnitude, or a scalar? Also, are you measuring the instantaneous value (DC value), or the range of variation (AC value) of the quantity? If AC is chosen, there are various ways to measure this number (RMS, absolute average variation, peak-to-peak, peak negative or peak positive). With AC, frequency range is also an important consideration, as well as the averaging time. In our project we are measuring the instantaneous value (DC value).

5.1 SCANNER IN INDUSTRY In industry, dependence on a single display is usually avoided. A single quantity is displayed on 2 to 3 different displays. It is due to the reason that an electronic error may occur in single display’s reading & if operator is dependent on a single display it will be dangerous and even if process is full of hazards (like in nuclear reactions or boiler’s temperature/pressure) then dependence on a single display will be a fool. So in our project we have used two displays. One is software based (HMI) and second one is discussed here that is digital scanner. Digital scanner are also getting importance due to the reason that a single display shows all the quantities and need for multiple displays is vanished.

5.2 REQUIRED FEATURES We wanted to design a digital scanner for displaying the three industrial parameters (temperature, level & position) .A single display was to used to show the three quantities which was to be done by using the time sharing /multiplexing __________________________________________________________________ PCSIR - Institute of Industrial Electronics Engineering, IIEE ST-22/C, Block-6 Gulshan-e-Iqbal, Karachi – 75300

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technique. One quantity was to be displayed at a time and after set time next quantity

would appear and so on. After last quantity appearance cycle would be repeated. Set time for appearance of quantities could be changed (increase or decrease) externally by operator & scanning could be stopped by operator at appearance of any particular quantity. Moreover operator could be jumped at any required parameter if he wanted.

5.3 AVAILABLE DESIGNING TECHNIQUES There are different techniques available for designing digital scanner. The adopted design depends on designer’s technical approach. But at system level there were two possible solutions to achieve desired goal in our mind. (I)

Complete embedded system

(II)

Partial embedded system The detail of selected and rejected design is given following.

5.3.1 COMPLETE EMBEDDED SYSTEM An embedded system or complete embedded system is one in which whole system is designed on a single chip which is usually a programmable chip like microcontrollers and microprocessor based systems. Embedded systems are designed for performing dedicated tasks and these systems work on the principles of digital computers. All those functions, which are performed by different external components in an un-embedded system, are performed on a single chip by using different programming techniques. For a complete embedded system based digital scanner beside other basic requirements we required a programming device with following built-in features: •

Require at least 10bit microcontroller system.

•

Three analog input channels.

•

Also 10bit ADCs built-in into the microcontroller Still having all above features we had to perform scaling externally.

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5.3.2 PARTIAL EMBEDDED SYSTEM A partial embedded is one in which both embedded and un-embedded features are merged. In this system designer divide his tasks into two groups, one suitable for embedded system and other suitable for un-embedded system. It is not necessary to perform all tasks on a single chip because some tasks can be performed externally better and easier as compare to on a programmable chip. So if we design scanner using partial embedded system we require following feature in programmable chip. •

8bit architecture like AT89s51 is enough.

•

No analog input channel is required.

•

No built-in ADC is required because analog-to-digital conversion is performed outside controller.

5.4 SELECTED DESIGN Due to more flexibility in partial embedded system we choose this one. Besides flexibility following are the main advantages of partial embedded system. •

Awareness with technology.

•

All required components are available in market.

•

High accuracy/linearity in reading is easily achievable.

•

Trouble shooting is easy and economical. The detail of implemented is given in following sub headings.

5.4.1 DESIGN IMPLEMENTATION As our required input channels were three so we implemented our design using scaling, analog Mux, 7-segment decoder, millivolts measuring IC etc as shown in block diagram of digital scanner.[ figure: 5.1].Circuit diagram of the same system is given on next page in figure:5.2 __________________________________________________________________ PCSIR - Institute of Industrial Electronics Engineering, IIEE ST-22/C, Block-6 Gulshan-e-Iqbal, Karachi – 75300

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Figure -5.2: Circuit Diagram of Digital Scanner

Figure 5-1: Block diagram of digital scanner.

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10k

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P2.0/A8 P2.1/A9 P2.2/A10 P2.3/A11 P2.4/A12 P2.5/A13 P2.6/A14 P2.7/A15

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Figure 5-2: Circuit schematic of digital scanner

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5.4.2 DESCRIPTION OF SYSTEM BLOCK DIAGRAM The detail of system block diagram shown in figure-5.1 is given as follow: (I) Scaling As shown in block diagram that three quantities after signal conditioning comes at scaling card’s input. The designed scanner is a versatile scanner which can be used for any three parameters whose upper limit lies within the range of three digits that is 999.So here the purpose of scaling is to adjust the upper limit of all quantities individually. We adjusted the first channel for 260, second channel for 600 and third channel for 100 respectively for level (in mm), temperature (in oC) and position (in %).

(II) Analog Multiplexer After scaling, three signals are given to the input of analog multiplexer. Analog multiplexer gives one signal at output at a time after selecting from three input signals according to the selection code given at selection pins. The two selection pins of the analog multiplexer are controlled here by microcontroller.

(III) Digit Selector and BCD Converter Actually it is an analog-to-digital converter for 3 digit display. It accepts one analog input and converts it into digital BCD code. It provide multiplexed BCD output with three bits reserved for digit selection that is to what digit(MSB,NSB or LSB) present BCD code belongs. This digit selection bit is used for activating the particular transistor which further activates the relevant 7-segment. More deeply the actual display circuit is a voltmeter which measure 000mv to 999mv linearly. As our sensor/transducer output is greater than one volt so we used scaling to decrease voltage level by decreasing the gain of amplifier and set the Maximum range of all physical quantities at display by adjusting gain of all quantities.

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(IV) Microcontroller and Selection Panel As we have already discussed that the selection bits of the analog multiplexer is controlled by a microcontroller so the switching speed is control here by using an eight bit microcontroller AT89C51. When user interacts with selection panel, Microcontroller does the following task. •

Display reading can be stopped at particular appearance by pressing STOP button.

•

Display reading can be start (continue) from that stopped particular appearance by pressing START button.

•

Display can be reset by pressing RESET button. After pressing reset button display will start from very first quantity whatever at any quantity it is.

•

Sequence time can be increased by pressing INCREASE button.

•

Similarly sequence time can be decreased by pressing DECREASE button.

•

Operator can jumped at any position by first pressing STOP button and then required quantity number as P.1, P.2 or P.3.

• (V) Position Segment We used three 7-segment displays to show 3-digits however there is also another 7-segment. Before clearing the presence of this segment one question arises in mind. When different quantities appear at display, how will operator / viewer will recognize that to which physical quantity this reading belongs? The answer to above question is that the single 7-segment shows arithmetic digit with changing sequence of physical quantities at display. This arithmetic digit shows particular quantity as defined by the installer of hardware display. Here we set this display to show the following digits for particular quantities. •

Appearance of 1 shows the level.

•

Appearance of 2 shows the temperature

•

Appearance of 3 shows the position

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5.5 PROGRAM FLOWCHART Intrpt(STP) Start

Strt

A= 0

N Reti

Strt =1

P1=A

Y T+

Dly1500ms

Inc A T-

Y

P.1

Y

N

Y

N A=03

T=1

Dly +

N P.2

Y N

Y P.3 = 1

T+=1

N

A=04

P.3

Y

P.2 =1

P.1 =1

Dly -

A=01

N A=02 Figure-5.3: Controller Program flowchart.

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5.6 POSSIBLE IMPROVEMENTS Whatever perfect is a thing, there is always a need for changing and improvements and present day scientific world is the result of these changing and improvements. Those possible improvements which are possible in our designed scanner are given below in detail.

5.6.1 Addition of New Input Channels We have designed this scanner for three channels according our requirement. However the number of input channels can be increased up to user requirement using the same technique. In industry hundreds of different parameters are to be measured at a time. Another reason of using partial embedded was that in complete embedded system we can not have a microcontroller with hundreds of analog inputs so in complete embedded system we have to use multiplexing externally. In our selected design new input channels can be increased by just replacing the analog multiplexer, with one which has user desired number of input channels, and some changing in controller’s program.

5.6.2 INCREASING UPPER RANGE The display in our designed scanner is limited to three digits. In our project the maximum upper range was 600 for temperature which lies in three digits so we designed scanner with maximum of 999 upper ranges. However upper range can be increased up to 999…N as per user requirement by adding new 7segments.Designer have modify the basic circuit of display for achieving this task.

5.6.3 ADDITION OF NEW FEATURES Besides available features new features can be added if necessary .Actually we have added almost all required features for digital scanner. However other features, which make it more users friendly, can be added, like indication of __________________________________________________________________ PCSIR - Institute of Industrial Electronics Engineering, IIEE ST-22/C, Block-6 Gulshan-e-Iqbal, Karachi – 75300

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buzzer when any quantity exceeds its limit and LCD display can be used instead of seven segment display. By adding new features designer can convert this scanner into a data logging system.

5.7 SUMMARY In this chapter we introduce the reader with digital scanner and its importance in industry. After that we discussed about all available techniques for designing a digital scanner. Meanwhile we discussed in detail about the selected design including block diagram description. The advantages and disadvantages of both complete and partial embedded system are discussed. The detailed description of block diagram was also given. In the end we discussed about the available features and possible improvements in the designed scanner. Some possible improvements examples were also discussed here.

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INTRODUCTION This chapter describes the NI USB-6008 multifunction DAQ card hardware and software configuration using its setting techniques and driver software respectively according to the project requirement and developed human machine interface as a part of soft display. In addition a brief description of our self indigenously developed data acquisition card is also discussed since it has already been discussed that before getting national instruments hardware package we were developed our own DAQ card.

6.1 PROJECT REQUIREMENT Since in the project we have three physical parameters as liquid level, furnace temperature and servo controlled valve position. After signal conditioning of all these parameters we have 0-5 volts which has to be fed up into the DAQ card. Therefore it must have at least three analog inputs for all three parameters to be displayed. In indigenously developed DAQ card we have three analog input channels as per project requirement. But after getting the NI USB-6008 DAQ card we have added also the control features in our project. Therefore to control the valve position we require at least one analog output for the desired reference position and one digital output to actuate the water pump in order to maintain the required liquid level in the tank. So it can be summarized that DAQ card must have following minimum features as our project requirements. •

Three Analog Inputs channels.

•

One Digital Output Channel.

•

One Analog Output Channel.

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6.2 INDEGENOUSLY DEVELOPED DAQ CARD Data acquisition card is responsible for taking input signals, process it, and make compatible for PC for analysis, database and display (user interface). Self designed data acquisition card has three analog input channels and serially communicated with the PC through com port at a rate of 9600 bps. This card has 8-bit resolution ADC to convert data into digital signals. The card block diagram is shown in figure 6-1.

Level Temp:

Analog Mux

ADC

Micro Controller

Serial Interface

To Computer

Position

Select Logic

Figure-6.1: The block diagram of indigenously developed DAQ card. The parameter to be processed and displayed will be selected by the controller from select logic.

6.2.1 MUXING Analog mux is used at the first stage for selecting a single quantity out of three parameters at a time and switching them frequently. Since all of the parameters are slowly varying so switching speed is not a problem. In the circuit design we have used dual four channel analog mux so that this card can be extended up to four channels with just a single connection and simple addition of command in the controller program.

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6.2.2 ANALOG TO DIGITAL CONVERSION The single output from mux is fed up to 8-bit ADC. The resolution is restricted due to microcontroller. We used here a successive approximation fast ADC having conversion rate of just 100 micro seconds which is high enough for the selected parameters. All the control signals of ADC are controlled by the microcontroller.

6.2.3 MICROCONTROLLER The microcontroller is responsible for three matters. First selecting the desired channel of the mux by giving logics to its select pins. Secondly to control the ADC and receive data from it and third to transmit data serially to the computer by giving the signal of selected channel as well.

6.2.4 SERIAL INTERFACING The controller transmits and receives signal through its UART, since we have used RS-232 standard serial communication for which it requires a line driver in order to make compatible the controller signals with RS-232 standard. The transmission is configured at a baud rate of 9600 bits per second. The handshaking signals of com port (DB-9) are not utilized because the selected microcontroller does not supports it.

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ALE/PROG PSEN

P3.0/RXD P3.1/TXD P3.2/INT0 P3.3/INT1 P3.4/T0 P3.5/T1 P3.6/WR P3.7/RD

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Figure 6-2: Circuit schematic of indigenously developed data acquisition card.

__________________________________________________________________

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6.3 NI USB-6008 MULTIFUNCTION DAQ CARD The card was import so that a complete virtual instrumentation system can be developed by using modular hardware and customizable application software. Before selecting the DAQ card it was obligatory that it must fulfill the project requirement as described earlier in detail but also it should be low cost, easy configurable and the most of important that was in our mind that it must be capable to be used in different labs of the institute like control, instrumentation, PLC and electronics lab so that students may adequate of virtual instrumentation by using embedded multifunction data acquisition card and can perform their course practical.

Therefore we have selected the NI USB-6008 multifunction data acquisition card as it offers all the features that we required but also included the complete student kit so that a virtual instrumentation system may be developed within minutes as it includes a free LabVIEW student edition as well.

6.3.1 FEATURES •

Small and portable

•

12 or 14-bit input resolution, at up to 48 kS/s

•

Built-in, removable connectors for easier and more

cost-effective

connectivity •

2 true DAC analog outputs for accurate output signals

•

12 digital I/O lines (TTL/LVTTL/CMOS)

•

32-bit event counter

•

Student kits available

•

OEM versions available

ANALOG INPUTS •

Number of channels.......8 single-ended/4 differential

•

Type of ADC... Successive approximation

•

ADC and DAC resolution .......12 bits

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ANALOG OUTPUTS •

Number of channels........... 2

•

Maximum update rate150 Hz, software-timed

DIGITAL I/O •

Number of channels..................12

•

Direction control: Each channel individually programmable as input or output

32 BIT COUNTER BUS TYPE: USB PLUG N PLAY CONNECTIVITY

Figure 6-3: NI USB-6008 multifunction DAQ card. The complete description can be taken from appendix 10-A.

This card is based upon the same techniques as we utilized in the self developed DAQ card. It multiplexes all the input channels at a maximum sampling rate of 10KS/s. The complete block diagram of the card is shown in figure 6-4.

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Figure 6-4: The block diagram of NI SUB-6008 multifunction DAQ card

6.3.2 HARDWARE SETUP Install combicon screw terminal blocks by inserting them into the combicon jacks. Then apply the signal labels to the screw terminal blocks for easy signal identification and connect the wiring to the appropriate screw terminals. Now device is ready just plugging USB cable with both the PC and device. All these steps cab simply be followed as shown in figure 6-5.

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Figure 6-5: Setting up hardware. Complete description can be taken from manual in appendix 10-A.

6.4 GETTING STARTED STEPS There are certain steps which have to be followed before using the device in order for proper configuration and functioning. The followed steps describe how to install and configure the NI-DAQmx (driver software for NI USB-6008) and USB data acquisition device and how to verify the device is working properly.

Step 1. Install the Application Software Install you NI application software that is LabVIEW 8.2.1, shipped with the kit. If you have an existing application written with an earlier version, make a backup copy of the application. You then can upgrade your software and modify the application.

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Step 2. Install NI DAQmx Software This software must be installed before connecting the device with computer so that the system can detect and install the device whenever it is plugged with the PC

Step 3. Set Up the Device Set up the device as described under the heading of hardware set up and follow those steps. Treat the DAQ device as you would any static sensitive device. Always properly ground yourself and the equipment when handling the DAQ device or connecting to it.

6.5 DEVICE RECOGNITION Before attaching the signal lines first we have to check either the system has recognized the device

or

not.

For

the

purpose

open

measurement and automation (max) software and expand devices and interfaces and further expand NI DAQ-devices.

Check that your

device appears under devices and interfaces as shown in figure 6-6. Highlight your recognized device right click it and select self test as shown in figure 6-7. When the self test finishes a message

Figure 6-6: Device recognition tree in max.

indicates successful verification or if an error occurred.

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Figure 6-7: Device self test. A success message will be displayed if device pass the self test as shown.

6.5.1 ATTACH SENSORS/SIGNAL LINES Attach sensors and signal lines to the terminal block as described in the figure 6-8. For signal lines and sensor information, refer to manual in appendix 10-A. DAQ assistant is accessible from MAX or LabVIEW to configure virtual channels and measurement tasks. We will use and configure it in LabVIEW in the next chapter as a part of G-Programming.

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Figure 6-8: Attaching sensors/signal lines with the device to the selected channels and setting up timing and triggering from software.

6.6 SUMMARY In this chapter we discussed the national instruments USB data acquisition device selection criteria in detail according to the project requirements and future enhancements and described in detail that how a USB DAQ device is configured for proper operation by mentioning different steps of hardware setting, device recognition, and self test and how sensors/signal lines are attached with the device. Then provided complete features of selected NI USB-6008 multifunction DAQ card. In addition the self indigenously data acquisition card was also discussed briefly giving its designing techniques.

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INTRODUCTION Human machine interface is the aggregate of means by which peoples (the user) interact with a particular machine, device, computer program, or other complex tool (systems). The interface provides means of •

Inputs: Allowing the users to manipulate a system

•

Outputs: Allowing the system to produce the effects of the users' manipulation. To work with a system, the users need to be able to control the system and

assess the state of the system. User interfaces has great significance in the industrial instrumentation and automation. All the parameters which have to be measured are displayed on the computer based interfaces in the control rooms in every modern industry which refers to the graphical, textual and auditory information the program presents to the user, and the control sequences (such as keystrokes with the computer keyboard, movements of the computer mouse, and selections with the touch screen) the user employs to control the program, provided articulated graphical output on the computer monitor. There are at least two different principles widely used in GUI design: Object-oriented user interfaces and application oriented interfaces. Under the hood, there are several software components that work together to do the job like visual basic, C/C++, matlab etc. We have developed our project HMI on the industry standard LabVIEW. This chapter deals with the programming environment, advantages and applications of LabVIEW and provides comprehensive sketch of the developed HMI.

7.1 LabVIEW The National Instruments LabVIEW graphical development environment helps create flexible and scalable design, control, and test applications. With LabVIEW, engineers and scientists can interface with real-world signals; analyze data for meaningful information; and share results through intuitive displays, reports, and the Web. __________________________________________________________________ PCSIR - Institute of Industrial Electronics Engineering, IIEE ST-22/C, Block-6 Gulshan-e-Iqbal, Karachi – 75300

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Short for Laboratory Virtual Instrumentation Engineering Workbench is a platform and development environment for a visual programming language from National Instruments. The graphical language is named "G". Originally released for the Apple Macintosh in 1986, LabVIEW is commonly used for data acquisition, instrument control, embedded design and industrial automation on a variety of platforms

7.1.1 DATAFLOW PROGRAMMING The programming language used in LabVIEW, called "G", is a dataflow language. Execution is determined by the structure of a graphical block diagram (the LV-source code) on which the programmer connects different function-nodes by drawing wires. These wires propagate variables and any node can execute as soon as all its input data become available. Since this might be the case for multiple nodes simultaneously, G is inherently capable of parallel execution. Multi-processing and multi- threading hardware is automatically exploited by the built-in scheduler, which multiplexes multiple OS threads over the nodes ready for execution.

Figure 7-1: Screenshot of a simple LabVIEW program [Courtesy of NI website] __________________________________________________________________ PCSIR - Institute of Industrial Electronics Engineering, IIEE ST-22/C, Block-6 Gulshan-e-Iqbal, Karachi – 75300

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Screenshot of a simple LabVIEW program in figure 7-1 that generates, synthesizes, analyzes and displays waveforms, showing the block diagram and front panel. Each symbol on the block diagram represents a LabVIEW subroutine (subVI) which can be another LabVIEW program or a LV library function [13].

7.1.2 GRAPHICAL PROGRAMMING LabVIEW ties the creation of user interfaces (called front panels) into the development cycle. LabVIEW programs/subroutines are called virtual instruments (VIs). Each VI has three components: a block diagram, a front panel and a connector pane. The latter may represent the VI as a subVI in block diagrams of calling VIs. Controls and indicators on the front panel allow an operator to input data into or extract data from a running virtual instrument. However, the front panel can also serve as a programmatic interface. Thus a virtual instrument can either be run as a program, with the front panel serving as a user interface, or, when dropped as a node onto the block diagram, the front panel defines the inputs and outputs for the given node through the connector pane. This implies each VI can be easily tested before being embedded as a subroutine into a larger program. The graphical approach also allows non-programmers to build programs by simply dragging and dropping virtual representations of the lab equipment with which they are already familiar. The LabVIEW programming environment, with the included examples and the documentation, makes it simpler to create small applications. This is a benefit on one side but there is also a certain danger of underestimating the expertise needed for good quality "G" programming. For complex algorithms or large –scale code it is important that the programmer possess an extensive knowledge of the special LabVIEW syntax and the topology of its memory management. The most advanced LabVIEW development systems offer the possibility of building stand alone applications. Furthermore, it is possible to create distributed applications which communicate by a client/server scheme, and thus is easier to implement due to the inherently parallel nature of G-code.

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7.1.3 ADVANTAGES One benefit of LabVIEW over other development environments is the extensive support for accessing instrumentation hardware. Drivers and abstraction layers for many different types of instruments and buses are included or are available for inclusion. These present themselves as graphical nodes. The abstraction layers offer standard software interfaces to communicate with hardware devices. The provided driver interfaces save program development time.

Peoples with limited coding experience can write programs and deploy test solutions in a reduced time frame when compared to more conventional or competing systems. Many libraries with a large number of functions for data acquisition, signal generation, mathematics, statistics, signal conditioning, analysis, etc., along with numerous graphical interface elements are provided

A main benefit of the LabVIEW environment is the platform independent nature of the G code, which is portable between the different LabVIEW systems for different operating systems (Windows, MacOSX and Linux).

7.2 DATA ACQUISITION TASKS In NI-DAQmx and LabVIEW, a task is a collection of one or more channels, timing, triggering, and other properties that apply to the task itself. Conceptually, a task represents a measurement or generation you want to perform. For example, you can create a task to measure temperature from one or more channels on a DAQ device. Traditional NI-DAQ Specific VIs for performing: • Analog Input • Analog Output • Digital I/O • Counter operations

NI-DAQmx Next generation driver: • VIs for performing a task • One set of VIs for all measurement types

Figure 7-2: Data acquisition task in LabVIEW [courtesy NI website] __________________________________________________________________ PCSIR - Institute of Industrial Electronics Engineering, IIEE ST-22/C, Block-6 Gulshan-e-Iqbal, Karachi – 75300

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The main advantage of data acquisition task in LabVIEW is that just a single set of VIs used to perform analog I/O, digital I/O, and counter operations where as other application software requires different platforms for each operation.

According to the project requirement we have to develop a task which should be the combination of three analog inputs for displaying all parameters, one analog output to control the servo valve position and a digital output to actuate the water pump at desired level.

DAQ assistant express VI is used in Gprogramming to develop the DAQ task. It interacts with the device through NI DAQmx. It quickly and easily programs the DAQ device by creating a local task. Most of the application can use this express VI. As it is placed in the block diagram from palate it will automatically pop up the configuration window. Now just follow these

Figure 7-3: DAQ assistant express VI

simple steps to develop the required task

1. Select the DAQ Assistant Express VI, shown in figure 7-3, on the Input palette and place it on the block diagram. The DAQ Assistant launches and a Create New dialog box appears. 2. Click the Analog Input button to display the Analog Input options. 3. Select Voltage to create a new voltage analog input task. The dialog box displays a list of channels available on DAQ device installed. The number of channels listed depends on the number of channels you have on the DAQ device. Here it will show eight channels for NI USB-6008. 4. In the My Physical Channels list box, select three physical channels to which the signals are connected, as ai0 for valve position, ai1 for liquid level, ai2 for furnace temperature, and then click the Finish button. The DAQ Assistant opens a new __________________________________________________________________ PCSIR - Institute of Industrial Electronics Engineering, IIEE ST-22/C, Block-6 Gulshan-e-Iqbal, Karachi – 75300

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window, shown in Figure 7-4, which displays options for configuring the channel you selected to complete a task.

Figure 7-4: DAQ device physical channels configuration window

5. In this configuration window select the input range of the signal from -10v to +10v; rename the selected channels, set the terminal configuration as single ended. In the timing section provide the acquisition mode as continuous samples ant fed 1K samples to read. Here we can select maximum 10K samples to read as supported by our device.

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Now this DAQ assistant express VI has been configured for the analog inputs. Place two more express VIs for analog and digital output respectively in the task. Repeat same procedure as discussed for configuration.

7.3 DEVELOPED HMI (THE FRONT PANEL) In the front panel different virtual instruments are developed for visual as well as numeric displays, for controlling parameters and giving diverse indications as well.

The meter gauge, liquid tank and the thermometer are placed for displaying visually, the servo valve position, height of liquid in the tank and furnace temperature respectively and all are calibrated according to the original mechanical model and real conditions. In addition to all these graphical VIs the numeric displays for all the three parameters in the units of closing percentage, millimeters and Celsius are also shown. Different indicators are placed which will alert the upper and lower limits of level and temperature.

For controlling purpose a knob is positioned to feed up the reference position for servo controlled valve. An indicator for the water pump on/off status is sited also while the status is controlled by the upper and lower limits automatically through programming.

There is an additional feature for database storage is developed on the front panel. This will store all the readings with respect to time in a file in the document format whenever and until the user wants to store the data in order to keep the record or taking printouts and graphs. A complete snap of the front panel is shown in figure 7-5 below where all the VIs placed can be viewed.

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Figure 7-5: The front panel of developed HMI on LabVIEW.

7.4 BLOCK DIAGRAM PROGRAMMING The graphical G-programming of LabVIEW was already discussed. The block diagrams of the programming are shown on the next page in figure 7-6 which is composed of different express VIs as listed under with their function description.

1. Split Signal Express VI: This express VI is used to split the different signals which are routed on the same line. Since DAQ assistant express VI yields only one output therefore it is required to split all the three signals for individual process and analysis.

2. Scaling and Mapping Express VI: __________________________________________________________________ PCSIR - Institute of Industrial Electronics Engineering, IIEE ST-22/C, Block-6 Gulshan-e-Iqbal, Karachi – 75300

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It is used to calibrate the acquired signal according to the real word.

3. Mathematical Comparison Express VI: Used for comparing scaled signals with the preset values in order for indicating different status and taking decisions for the controlling operations.

4. Write Measurement File Express VI: It is used for making database of the acquired information in different formats with many options.

5. Display Message to User Express VI: This express VI is used to display the messages to the user during run time under different conditions as programmed like if user wants to open the valve more than 100% then it will automatically pop up the massage of invalid range.

Besides these express VIs different Boolean and mathematical operations are utilized for manipulating and process the acquired signal and information as shown in figure 7-6 which gives a complete look of block diagram programming. Here it can be seen that all the express VIs and operations are placed within a loop named as while loop. This loop is always placed before starting the program and all the express VIs and sub pallets are placed within this loop to ensure the continuous operation otherwise either it will stop immediately or will not execute.

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Figure 7-6: Block diagram programming of developed HMI using LabVIEW Gprogramming environment.

7.5 SUMMARY In this chapter first we described about the industry standard instrumentation software the LabVIEW and introduce its programming environment, discussed its applications and advantages over other programming languages. Then a complete scheme for configuring the data acquisition devices within LabVIEW was provided and created the local task to meet the project requirement using DAQ assistant express VI after which we acquired all the signals for further process, analysis and manipulation.

The developed HMI is then discussed including its front panel and block diagram programming in detail, giving description of all the express VIs and __________________________________________________________________ PCSIR - Institute of Industrial Electronics Engineering, IIEE ST-22/C, Block-6 Gulshan-e-Iqbal, Karachi – 75300

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operations used in its programming and the VIs that were customized in the front panel. All the features of HMI were provided.

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Our project began in July 2007 and at that time we did not even know where to start from! What kind of resources and effort are required to accomplish such tasks! But we took it as a challenge and from the day one we went through rigorous research and analysis, encountering a totally new and confusing problem at every step but by the grace of Allah we did not stop at any point and solved every problem on our own. Therefore, today we have achieved in this short span of six months what most people around us in this field have achieved in years. And we are proud of our effort. As explained earlier our task was to develop DAQ card and its HMI. To simulate this project practically we also require some input parameters so development of transducer to measure different physical parameters also become a part of our task. So we selected temperature, level and position as our physical parameters. We made different calculations to find out our required sensors and their signal conditioners and electronic devices for DAQ card. The details about these requirements are given in previous chapters. .WHAT WE ACHIEVED IN THIS PROJECT Indigenously development of transducers which gave us knowledge of internal working of industrial transducers. We developed J-type thermocouple of industrial standard which gave us knowledge that how industrial thermocouples are manufactured and what are the key points about which we have to care during thermocouple calibration for required output temperature reading. Our designed level transducer was not of industrial standard because cost was also our primary concerned but this designed transducer can replace industrial transducer for short time as it has no impact of high temperature and pressure environment. But finally we succeed in getting the industrial water column level transmitter which also provide us the hands on experience of calibrating and implementing the industrial transducers. Servo

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motors are widely used in the industry for lot of processes for position control. It has complex function but during our project we learned it thoroughly. Future of the industrial monitoring is the virtual instrumentation, the combination of customizable software (LabVIEW) and modular hardware (NI USB6008), is the most powerful tool for data acquisition and virtual instrumentation as it provides most user friendly environment, cost effective and quick to use. During the configuration of DAQ card and development of HMI on the LabVIEW we have faced a lot of problems; the main was unavailability of both the hardware, software and the peoples who worked on it. Till now it used rarely in our industries but during development of HMI we learned a lot about LabVIEW which will consequently help us in the future market.

ENHANCEMENTS There is common saying “nothing is permanent except change.” Therefore there are always the possibilities of improvements and enhancements in the previous design according to the current requirement and available resources and technology. We have made lot of efforts in designing our project in order to meet the peak but there are enhancements which can be carried out in the future. •

This project can be converted into wireless communication based monitoring system.

•

This project can be enhanced for the hundreds of inputs by using data networking communication protocols like Modbus, Ethernet etc.

•

Since our primary concern was the monitoring of parameters but we not only performed the instrumentation but also designed the control actions for position and pump control. But the DAQ has many vacant analog and digital IOs. These IOs can be employed by extending the mechanical assembly for

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more process parameters and control actions and modifying a little in the software.

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REFFERENCES [1] Application note NO: 369 for thermocouple signal conditioning, www.analog.com [2] Basic concept about designing of hardware display, http://www.electronicslab.com/projects/test/014/ [3] Components data sheet, http://www.datasheetarchive.com [4] Distributed control system, http://www.answers.com/topic/distributed-controlsystem?cat=technology [5] Floyd, Electronic Devices 6th Edition, Pearson Education, 2003 [6] Francis H Raven , Automatic Control engineering, McGraw-Hill, 1994 [7] HMI tutorials, http://www.iec.org/online/tutorials/hmi/ [8] Human Machine Interface, www.wikipedia.com./wiki/hmi [9] Industrial Text and Video Co., Electrical relay and Diagram Symbols Instrumentation Symbols and Identifications, www.industrialtext.com [10] ITS-90 Table for J-Type Thermocouple, ISE Incorporation http://iseinc.com [11] James W. Dally, Instrumentation for Engineering Measurement 2nd Edition, John Wiley & Sons Incorporation, 1993, p-110,124 [12] LabVIEW, www.wikipedia.com/wiki/labview [13] LabVIEW developer zone, www.ni.com/labview [14] Mohammad Ali Mazidi and Janice Gillispie Mazidi, The 8051 Microcontrollers and Embedded systems 8th Edition, Pearson Education, 2004, [15] Omega Engineering Technical Refference, Introduction to level Measurment, http://www.omega.com/toc_asp/sectionSC.asp?section=K&book=green&flag=1, 2006 [16] Ramakant A. Gaykwad, op-amps and Linear Integrated Circuits 3rd Edition, Prentice hall International, 1993 [17] Reference table of all types of thermocouples, http://instrumentationcentral.com/pages/thermocouple_reference_table.htm [18] Richard C. Dorf and Robert H. Bishop, Modern Control Systems 7th Edition, Addison Wesley [19] Robert T. Paynter, Introductory Electronic Devices and Circuits 4th Edition, Prentice hall Inc, 1989 [20] Scott Mackenzie, the 89c51 Microcontroller 2nd & Upgrade Edition

87 [21] Servo motors, http://www.epanorama.net/links/motorcontrol.html [22] Thermocouple modeling, web.cecs.pdx.edu/~gerry/epub/pdf/thermocouple.pdf [23] Group Discussion, www.groups.yahoo.com [24] Instrumentation, http://en.wikipedia.org/wiki/Instrumentation [25] Virtual Instrumentation, http://en.wikipedia.org/wiki/Virtual_instrumentation [26] Virtual & Traditional Instruments, http://zone.ni.com/devzone/cda/tut/p/id/4757 [27] Glossary, www.tdt.com/WebHelp/OX_FlashHelp/UserGuide/TipsTricks/Glossary.htm [28] Future of virtual instrumentation, http://www.scientificomputing.com/scwmayjun04james_truchard.html [29] Virtual Instruments in Engineering process http://zone.ni.com/devzone/cda/tut/p/id/4752 [30] Modern vs. Traditional Instrumentetation http://zone.ni.com/devzone/cda/tut/p/id/4757 [31] http://zone.ni.com/devzone/cda/tut/p/id/2964 [32] LabVIEW, http://www.ni.com/labview/whatis/

APPENDIX-B ASSEMBLEY CODE FOR 89S51 FOR DIGITAL SCANNER ; START PROGRAM ORG 00H LJMP MAIN ;**************************** ORG 0013H CHK_STRT: JB P2.0,CHK_INCR CALL DELAY_12MS JB P2.0,CHK_INCR RETI ;**************************** ORG 30H MAIN: MOV R5,#3 MOV P2,#0FFH MOV IE,#10000100B AGAIN_01: MOV A,#01H AGAIN: MOV P1,A CALL DELAY INC A CJNE A,#04H,AGAIN JMP AGAIN_01 ;***************************** CHK_INCR: JB P2.1,CHK_DECR CALL DELAY_12MS JB P2.1,CHK_DECR INC R5 JNB P2.1,$ JMP CHK_STRT ;****************************** CHK_DECR: JB P2.2,POS_1 CALL DELAY_12MS JB P2.2,POS_1 DEC R5 CJNE R5,#1,CONT_DEC MOV R5,#2 CONT_DEC: JNB P2.2,$ JMP CHK_STRT

; INTERRUPT 1 STARTS

; MAIN PROGRAM STARTS

; SUBROUTINE FOR INCRESING SCANNING TIME

; SUBROUTINE FOR DECRESING SCANNING TIME

;************************** ; SUBROUTINE FOR JUMPING AT POSITION 1 POS_1: JB P2.3,POS_2 CALL DELAY_12MS JB P2.3,POS_2 MOV A,#01H MOV P1,A JMP CHK_STRT ;************************** ; SUBROUTINE FOR JUMPING AT POSITION 2 POS_2: JB P2.4,POS_3 CALL DELAY_12MS JB P2.4,POS_3 MOV A,#02H MOV P1,A JMP CHK_STRT ;************************** ; SUBROUTINE FOR JUMPING AT POSITION 3 POS_3: JB P2.5,CHK_STRT CALL DELAY_12MS JB P2.5,CHK_STRT MOV A,#03H MOV P1,A JMP CHK_STRT ;************************** ; DELAY SUBROUTINE FOR SCANNING INC/DEC DELAY: MOV 31H,R5 Z: MOV R4,#5 Y: MOV R3,#200 X: MOV R2, #250 DJNZ R2 , $ DJNZ R3 , X DJNZ R4, Y DJNZ 31H , Z RET;************************ ; DELAY SUBROUTINE FOR MINIMIZING PUSH BUTTON BOUNCING DELAY_12MS: MOV R1,#25 T: MOV R0,#250 DJNZ R0,$ DJNZ R1,T RET END

APPENDIX-D: PROJECT MANUAL

MIDAS Multiplexed Industrial Data Acquisition System I. SIGNAL CONDITIONING AND CONTROLLING CARD FOR SERVO VALVE

INSTRUCTIONS 1) Only 0V to 5V should be given to reference for min. and max. Position of valve. 2) Adjust lower limit that is 0V output by varying Pot.1. 3) Adjust upper limit that is 5V output by varying Pot.2. 4) Adjust proportional gain by varying Pot.3.

NOTES: The above card not only used to measure position but also used for controlling the position of valve. __________________________________________________________________ PCSIR - Institute of Industrial Electronics Engineering, IIEE ST-22/C, Block-6 Gulshan-e-Iqbal, Karachi – 75300

II. LEVEL TRANSMITTER AND TEMPERATURE SIGNAL CODITIONING CARD

INSTRUCTIONS: 1) Pot.1 is used for adjusting load impedance for current out put transmitters. 2) Pot.2 is used for adjusting the gain of signal conditioned output of thermocouple. 3) Pot 3. is used as positive feedback gain for decreasing the non-linearity errors. 4) Pot 4. is used for adjusting the negative feedback gain during removing nonlinearity in thermocouple voltage. 5) Pot.5 is used for adjusting the ambient temperature. First short the thermocouple input and then adjust the ambient temperature. 6) Whenever thermocouple becomes open or power supply becomes higher than recommended then RED LED shown will automatically blinks.

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III. SCALING FOR DIGITAL SCANNER

INSTRUCTIONS: 1) Pot.1 is used for adjusting the upper limit of first quantity which is Level here. 2) Pot.2 is used for adjusting the upper limit of second quantity which is temperature here. 3) Pot.3 is used for adjusting the upper limit of third quantity which is Position of servo controlled valve here. NOTE: You can use any three quantities whose upper range falls within 999.

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IV. DIGITAL SCANNER

INSTRUCTIONS: 1) Pot.1 is used for adjusting the A/D conversion rate of scanner. 2) Pot.2 is used for adjusting the lower limit of the reading that is 000. 3) Pot.3 is used for same purpose as Pot.2 but it is more precise.

NOTES: Selection panel control the appearance of each parameters. scanning time can be increased or decreased by pressing button T+ or T- (500ms for each time) and can be jumped at any particular quantity by first pressing stop button and then required position. All three quantities after scaling is given at scanner input.

__________________________________________________________________ PCSIR - Institute of Industrial Electronics Engineering, IIEE ST-22/C, Block-6 Gulshan-e-Iqbal, Karachi – 75300