1. Operation of AC millivoltmeter
1. Observe the stop of the meter hand before powering on. If it is not on the surface zero scale, you need to adjust the mechanical zero position of the meter pointer.
2. Select input terminal I or II as required.
3. Put the range switch in the high range range, turn on the power supply, and use it after preheating for 10 minutes to ensure reliable performance.
4. Select the appropriate range according to the measured voltage. If the measured voltage is unknown, the range switch should be set to the maximum range, and then the range should be reduced step by step. It is advisable to deflect the needle to more than 2/3 of full scale, and then determine the voltage reading according to the scale indicated by the needle and the selected range.
5. When it is necessary to measure the voltage of the two ports, the two voltages to be measured can be fed to the input terminals I and II respectively, and the voltage reading of the I or II channel can be determined by toggling the input selection switch.
Note: It is normal for the pointer to oscillate a few times within 10 seconds after the power is turned on.
2. Notes on the use of AC millivoltmeter
1. Short-circuit zero adjustment before measurement. Turn on the power switch, clamp the red and black clips of the test line together, turn the range knob to the lmV range, and the pointer should be at the zero position. If the pointer does not point to the zero position, the test line should be checked for open circuit or poor contact, and the test line should be replaced.
2. The sensitivity of the AC millivoltmeter is high. After the power is turned on, the pointer will deflect due to the interference signal at a lower range, which is called a self-starting phenomenon. Therefore, when the signal is not tested, the range knob should be turned to a higher range to prevent the pointer from being bent.
3. When the AC millivoltmeter is connected to the circuit under test, the black clip should always be connected to the ground of the circuit to prevent interference.
4. When adjusting the signal, you should first turn the range knob to a larger range, change the signal, and then gradually reduce it.
5. Check the range knob and range mark are consistent before use. If the position is misaligned, a reading error will occur.
6. The AC millivoltmeter can only be used to measure the effective value of the sinusoidal AC signal. If the non-sinusoidal AC signal is measured, it must be converted.
7. The AC voltage block of the multimeter can not be used to replace the AC millivoltmeter to measure the AC voltage (the multimeter has a low internal resistance and is used to measure the power frequency voltage around 50Hz).