Hardware's Role In Virtual Instrumentation

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Visión General I/O plays a critical role in virtual instrumentation. To accelerate test, control, and design, I/O hardware must be rapidly adaptable to new concepts and products. Virtual instrumentation delivers this capability in the form of modularity within scalable hardware platforms. This document introduces a few of these platforms and modular I/O types and illustrates the .

Contenido 1. What are capabilities of virtual instrumentation hardware? 2. On which hardware I/O and platforms does virtual instrumentation software run? 3. How will new bus technologies such as USB 2.0 and PCI Express enhance virtual instrumentation? 4. What are the benefits of Ethernet for virtual instrumentation? 5. Additional Virtual Instrumentation Resources

What are capabilities of virtual instrumentation hardware? An important concept of virtual instrumentation is the strategy that powers the actual virtual instrumentation software and hardware device acceleration. National Instruments focuses on adapting or using high-investment technologies of companies such as Microsoft, Intel, Analog Devices, Xilinx, and others. With software, National Instruments uses the tremendous Microsoft investment in OSs and development tools. For hardware, National Instruments builds on the Analog Devices investment in A/D converters. Fundamentally, because virtual instrumentation is software-based, if you can digitize it, you can measure it. Therefore, measurement hardware can be viewed on two axes, resolutions (bits) and frequency. Refer to the figure below to see how measurement capabilities of virtual instrumentation hardware compare to traditional instrumentation. The goal for National Instruments is to push the curve out in frequency and resolution and to innovate within the curve.

Figure 1. Compare virtual instrumentation hardware over time to traditional instrumentation. See Also: Learn about NI data acquisition hardware Learn about NI modular instrumentation hardware

On which hardware I/O and platforms does virtual instrumentation software run? National Instruments modular I/O covers diverse I/O types so that engineers and scientists can select I/O across many categories including analog, digital, counter/timer, image, and motion. Modular I/O also includes modular instruments such as oscilloscopes, meters, arbitrary function generators, LCR meters, and more. With the wide variety of excellent I/O, engineers can randomly select any I/O type required by the application. Careful engineering ensures that these diverse I/O types work seamlessly together, meaning they can efficiently share backplane and timing resources. Standard hardware platforms that house the I/O are important to I/O modularity. Laptop and desktop computers provide an excellent platform where virtual instrumentation can make the most of existing standards such as the USB, PCI, Ethernet, and PCMCIA buses. Using these standard buses, National Instruments can focus on measurement hardware innovation while benefiting from inevitable PC platform innovation (for example, USB 2.0 and PCI Express).

Figure 2. Modular I/O and scalable platforms such as USB, PCI, and PXI provide flexibility and scalability. In addition to supporting standard platforms, National Instruments is part of a 65-vendor consortium that has helped tailor the PXI hardware platform for virtual instrumentation. PXI is a standard for modular I/O built on PC technologies. It adds integrated timing and synchronization, industrial ruggedness, and increased channel count to a PC-based architecture. Today, there are more than 1000 products created for the PXI platform being used worldwide by thousands of companies. Choosing the appropriate platform on which to create virtual instrumentation on depends on specific application requirements. For example, portability, stringent synchronization, and acquisition rates all play a role in choosing a platform.

[+] Ampliar Imagen Table 1. National Instruments Hardware Platform Comparison See Also: Learn about the PXI hardware platform Learn about the USB hardware platform Learn about the Compact FieldPoint hardware platform Learn about the CompactRIO hardware platform

How will new bus technologies such as USB 2.0 and PCI Express enhance virtual instrumentation? Virtual instrumentation uses advances in commercially available computer technologies to make faster and higher-performance measurements at lower cost than traditional instruments. One example of this is with PC data buses. While instrument communication interfaces such as serial and GPIB have remained virtually unchanged for decades, new PC buses provide dramatic improvements in bandwidth and ease of use. Since the mid-1960s, PC processing power has, according to Moore’s Law, approximately doubled every 18 months. Now, data buses such as PCI Express and USB 2.0 are making similar leaps in speed. Good virtual instrumentation software takes advantage of these new technologies while minimizing the impact on the application. The 132 MB/s bandwidth provided by the 32-bit, 33MHz PCI bus still present on most desktop PCs was a good match for plug-in peripherals 10 years ago, but now can be monopolized by a single device, such as a Serial-ATA drive. And Gigabit LAN cards – at 1000 Mb/s – use approximately 95 percent of available PCI bandwidth. PCI bus architecture requires it to share the available 132 MB/s with all devices on the bus, so high-bandwidth devices such as Serial-ATA drives and Gigabit LAN cards strangle other devices on the PCI bus. To remedy these limitations, a new peripheral bus called PCI Express has recently started to appear in new PCs. PCI Express maintains software compatibility with PCI, but replaces the physical bus with a high-speed (2.5 Gb/s) serial bus. Data is sent in packets through transmit and receive signal pairs called lanes with about 200 MB/s bandwidth per direction, per lane. Multiple lanes can be grouped together into x1 (“by-one”), x2, x4, and x8 lane widths. Unlike PCI, which shares bandwidth between all devices on the bus, this bandwidth is provided to each device in the system. PCI Express benefits for virtual instrumentation are obvious. Plug-in devices such as data acquisition devices and frame grabbers can use the increased bandwidth for faster acquisitions and higher throughputs, and multiple system devices benefit from guaranteed bandwidth availability.

Figure 3. The Evolution of PC Bus Technologies USB 2.0, now standard on all new desktop and laptop PCs, also offers significant benefits to virtual instrumentation. Initially created to connect peripherals such as keyboards and mice to the PC, USB has quickly become the ubiquitous standard for sending data to and from the PC and electronic devices, including digital cameras, MP3 players, and even data acquisition devices. The USB plug-and-play

nature makes usability and device portability extremely simple. The PC automatically detects when a new device has been plugged in, queries for device identification, and appropriately configures the required drivers. In addition, USB is hot-pluggable, so, unlike other data buses, there is no need to power down the PC before adding or removing a device. The high speed of USB 2.0 improves data throughput by 40X compared to USB 1.1, increasing bandwidth to 480 Mb/s. All new PCs come with USB 2.0 ports, and PCI Express is emerging as the new plug-in bus standard. As Intel, Dell, HP, and other vendors continue to develop systems and components based on these technologies, economies of scale continue to improve performance and costs. Virtual instrumentation and National Instruments products will continue to use these bus technology advances to provide higher speed test and measurements products at even lower prices.

What are the benefits of Ethernet for virtual instrumentation? Virtual instrumentation systems frequently use Ethernet for remote test system control, distributed I/O, and enterprise data sharing. The primary benefit in using Ethernet is cost. In nearly all cases, the Ethernet network preceded the measurement system, so it often adds little cost to the measurement system itself. Ethernet provides a low-cost, moderate-throughput method for exchanging data and control commands over distances. However, due to its packet-based architecture, Ethernet is not deterministic and has relatively high latency. For some applications, such as instrumentation systems, the lack of determinism and high latency make Ethernet a poor choice for integrating adjacent I/O modules. These situations are better served with a dedicated bus such as PXI, VXI, or GPIB. Often, a virtual instrumentation system uses other buses in conjunction with Ethernet. Typically, a network node consists of modular I/O clusters. Each cluster uses a high-speed, low-latency bus to exchange data between different I/O modules. To communicate with neighboring nodes, transfer data to a remote location, or accept commands from a remote location, the network nodes use the Ethernet network.

Figure 4. Example of Ethernet/LAN based virtual instrumentation system

Additional Virtual Instrumentation Resources To learn more about virtual instrumentation, use the following resources: • • • • •

About Virtual Instrumentation Virtual Instrumentation versus Traditional Instruments Virtual Instrumentation for Test, Control, and Design Software's Role in Virtual Instrumentation Hardware's Role in Virtual Instrumentation