1. ECE 201 Circuit Theory I1 Measuring Voltage and Current d’Arsenval analog meter movement

2. ECE 201 Circuit Theory I2 Analog Ammeter Use a d’Arsenval meter movement with a parallel resistor (shunt). The parallel resistor diverts some of the current away from the meter movement.

3. ECE 201 Circuit Theory I3 Analog Voltmeter Use a d’Arsenval meter movement in series with a resistor (multiplier). The resistor limits the voltage drop across the meter movement.

4. ECE 201 Circuit Theory I4 Sources of Error Any instrument (meter) used to make measurements extracts energy from the circuit. (Known as “loading” the circuit). The amount of error due to loading depends on the effective resistance of the instrument compared with the resistance in the circuit.

5. ECE 201 Circuit Theory I5 Rule of the “one-tenth” The effective resistance of the ammeter should be no more than 1/10 th of the value of the smallest resistance in the circuit. –The current being measured should be the same with or without the ammeter.

6. ECE 201 Circuit Theory I6 For a Voltmeter Since voltage is a parallel measurement, the “loading” effect is minimized when the voltmeter resistance is much higher than the circuit resistance across which the measurement is being made.

7. ECE 201 Circuit Theory I7 Problem # 3.32 An ammeter with a resistance of 5Ω is used to measure the current i o in the circuit. What is the % error in the measured value?

8. ECE 201 Circuit Theory I8 ioio

9. 9 Problem # 3.33 A d’Arsenval voltmeter is shown. Determine the value of R v for a full-scale reading of 5 Volts.

10. ECE 201 Circuit Theory I10 Choosing the Multiplier Resistor When 5V is applied, the meter will be at full-scale deflection. The meter resistance is 50Ω. Total resistance needs to be 5kΩ. The series resistor R v (multiplier) needs to be 4950Ω.

11. ECE 201 Circuit Theory I11 Problem # 3.34 The d’Arsenval voltmeter described in Problem # 3.33 is used to measure the voltage across the 24Ω resistor.

12. ECE 201 Circuit Theory I12 What will the voltmeter read? What is the % error in the reading?