Tutorial 1

Tutorial 01

DC Ammeter Example 2-2 A 200-µA meter movement with an internal resistance of 550-Ω is used in 0- to 500-mA ammeter. Find the value of the required shunt resistance.

Ayrton Shunt Im Rm

I - Im

Rc

Rb

Ra

I2 I3

I1

I

+

-

Fig. 3: An Ammeter using Ayrton shunt.

Example 2.3: Compute the value of the shunt resistors for the circuit. Given that Rm = 1.2kΩ, Im =150 µA, I1=5mA, I2=50mA, I3=200mA. Check : Rsh = Ra + Rb + Rc always!

Ammeter Insertion Effects Example 2.4: A current meter having an internal resistance of 100Ω is used to measure the current trough Rc in figure below. Determine the percentage of error due to the ammeter insertion. Given that Ra=Rb=Rc= 2.2kΩ

Ra

E = 5V

Rb

Rc

DC Voltmeter Example 3. • Calculate the values of Rs for the multiplerange DC Voltmeter circuits as shown below:but change the range to 3mV, 3V and 300V.

Rm = 2 kΩ

Ifs = 100µA Rs1

3mV

Rs2

Rs3

3V

300 V

+ -

DC Voltmeter Example 4. • Calculate the values of Rs for the multiplerange DC Voltmeter circuits as shown below: but change the range to 5mV, 5V and 100V.

Rc

Rb

Ra

Rm = 2 kΩ

Ifs = 50µA 5mV 5V 100V

+ -

Voltmeter Loading Effects Example 5:

• Two different voltmeters are used to measure the voltage across RB in the circuit below. The meters are: Meter A : S= 10kΩ/V;Rm=0.2kΩ; Range =5V Meter B : S=20kΩ/V;Rm=2.2kΩ; Range = 5V

Calculate: – Voltage across RB without any meter. – Voltage across RB when meter A is used. – Voltage across RB when meter B is used. – Loading Errors in both voltmeter readings.

RA

10kΩ

RB

1.8kΩ

E = 20V

Voltmeter Loading Effects Example 6: • Find the voltage reading and the percentage of loading error of each reading obtained with a voltmeter on: E = 20V – Its 10-V range. – Its 50-V range – Its 200-V range. The meter has a 30-kΩ/V sensitivity and connected across RA.

RA

2.2kΩ

RB

8.2kΩ

Ohmmeter • Find the value of R, ¼ scale, ½ scale and ¾ scale of this Ohmmeter?