Calibration of Permanent-Magnet Moving Coil aka PMMC Ammeter
Procedure for the Calibration of PMMC Ammeter:-
- Give the connections as per the circuit diagram.
- By adjusting the supply voltage make that the ammeter shows a current of 0.1 Amps
- Now measure the voltage across the shunt by using a potentiometer.
- Determine the current through the shunt by dividing potentiometer reading by shunt resistance (0-1Ω).
- Draw the calibrations curve which is drawn between %error Vs measured indication. The expected graph is as follows:
- Repeat the same for different current curves with the only precaution of making connections with due care of polarity and tabulate the results. The expected example results are as given in the below table.
| S.No |
Ammeter Reading |
Pot. Reading (V) |
Standard Resistance |
Measured Reading (A) |
% error |
| 1. |
0.51 |
0.043 |
0.1 |
0.43 |
15.681 |
| 2. |
0.61 |
0.053 |
0.1 |
0.53 |
13.11 |
| 3. |
0.7 |
0.061 |
0.1 |
0.61 |
12.85 |
| 4. |
0.89 |
0.0775 |
0.1 |
0.775 |
12.92 |
| 5. |
1.00 |
0.0875 |
0.1 |
0.875 |
12.5 |
➤
