Several Experiences in Using Multimeters
1. Before use, it is necessary to check whether the function conversion switch is in the corresponding position of the measured power and whether the probe is in the corresponding socket.
2. According to the requirements of the "grounding" or "arrow" symbol on the meter head, if the pointer of the multimeter is not pointing to the starting point of the scale, the mechanical zero position should be adjusted first.
3. Select the appropriate range based on the size of the measured electricity. When measuring voltage and current, try to deflect the pointer to more than 1/2 of full scale to reduce testing errors. If you don't know the size being measured, you can first measure with a large range and gradually reduce the range until the pointer has a significant deviation. But when testing high voltage (above 100 volts) or high current (above 0.5 amps), the range should not be changed with electricity, otherwise it may cause the switch contacts to ignite and burn candles.
4. When measuring DC voltage or DC current, pay attention to the polarity of the measured object. If you don't know the voltage level of the two points being measured, you can briefly touch these two points with the two probes, determine the potential level based on the direction of the pointer impact, and then measure again.
5. When measuring AC voltage, it is necessary to determine whether the frequency of the AC voltage is within the operating frequency range of the multimeter. Generally, the operating frequency range of a multimeter is 45-1500Hz. If it exceeds 1500Hz
The measured reading value will sharply decrease. The AC voltage scale is based on the effective value of sine waves, so a multimeter cannot be used to measure sine wave voltages such as triangular waves, square waves, sawtooth waves, etc. When there is a DC voltage superimposed on the AC voltage, a DC blocking capacitor with sufficient withstand voltage should be connected in series before measurement.
6. When measuring the voltage on a certain load, it is necessary to consider whether the internal resistance of the multimeter is much greater than the load resistance. If not, due to the shunt effect of the multimeter, the reading value will be much lower than the actual value. In this case, the multimeter cannot be directly used for testing, and other methods should be used instead. The internal resistance of the multimeter voltage range is equal to the voltage sensitivity multiplied by the full voltage value, such as MF
-The sensitivity of a 300000 meter in the DC100 voltage range is 5 kiloohms, and the internal resistance in this range is 500 kiloohms. Generally speaking, the internal resistance is small in the low range range range and large in the high range range range. When testing a certain voltage in the low range range, if the internal resistance is small and the shunt effect is large, it is advisable to switch to the high range range test. This way, although the pointer deflection angle is small, the accuracy may be higher due to the small shunt effect. There is a similar situation when measuring current. When a multimeter is used as an ammeter, the internal resistance of a large range is smaller than that of a small range.
