Expt3.Extension of Ammeter Range PDF

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Extension of Ammeter Range...

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Electrical Measurements Lab Expt No: 3

2019

Date:

EXTENSION OF AMMETER RANGE

Aim  To extend the range of the given (0-100) mA moving coil ammeter to read up to 250mA.

Apparatus required Sl.No 1.

Instrument Ammeter (MC)

Range 0-500 mA

Quantity 1

2.

Ammeter (MC)

0-100 mA

1

3.

Rheostat

4.

Digital multimeter

1 1

0-20V

Circuit Diagram

Amrita School of Engineering, Amritapuri, EEE Department

Page:

Electrical Measurements Lab

2019

Procedure: 1. Make the circuit connections as shown in fig. 2. Keep the rheostat at the maximum resistance position and DC voltage at minimum. 3. Switch on the power supply (30 V) and set the current as 100mA in Ammeter whose range is extended to 250mA by adjusting the rheostat. 4. Measure the voltage across the ammeter using DMM 5. Calculate the ammeter internal resistance R as V/i, where i=100mA 6. Calculate the shunt resistance that has to be added to extend the range of ammeter. 7. Connect the shunt resistance across the test meter. 8. By adjusting the load resistance RL, take a few readings of ammeter A and the milli ammeter whose range is being extended. 9. Verify the readings by comparing the readings of ammeter A with the corresponding milliammeter reading multiplied by the multiplying factor. Record your observations and results in tabular form. Tabular column: a) To find the internal resistance of test ammeter. Sl No.

Voltage (V)

Current (A)

Resistance (Ω)

b) Extension of range of ammeter. Amrita School of Engineering, Amritapuri, EEE Department

Page:

Electrical Measurements Lab Sl No

Standard reading (A)

2019

Ammeter Reading of meter under Multiplication factor test (A)

Result:

Amrita School of Engineering, Amritapuri, EEE Department

Page:...