Some Experience in Using a Multimeter
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 "ground" or "arrow" symbol on the meter head, place the multimeter vertically or horizontally. If the pointer does not point to the starting point of the scale, the mechanical zero position should be adjusted first.
3. Choose the appropriate range based on the size of the measured electricity. When measuring voltage and current, the pointer should be deflected to more than half of the full scale as much as possible to reduce testing errors. If you do not know the size of the measurement, you can first use * to measure a large range and gradually reduce the range until the pointer has a significant deviation. However, when testing high voltage (above 100 volts) or high current (0.5 amperes above 0), 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, attention should be paid to the polarity being measured. If you do not know the voltage of the two points being measured, you can briefly touch the two probes to 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 understand whether the frequency of AC voltage is within the working frequency range of a multimeter. Generally, the working frequency range of a multimeter is 45-1500Hz. Exceeding 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 wave sawtooth waves, etc. When there is a DC voltage superimposed on the AC voltage, a DC isolated 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 used directly for testing, and other methods should be used instead. The resistance within the voltage range of a multimeter is equal to the voltage sensitivity multiplied by the full scale 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 in the low range range is small, while the internal resistance in the high range range is large. When testing a certain voltage in the low range with a large shunt effect due to the small internal resistance, it is advisable to switch to the high range test. Although the pointer deflection angle is small, due to the small shunt effect, the accuracy may actually be higher. There is a similar situation when measuring current. When using a multimeter as an ammeter, the internal resistance of a large range is small, while the internal resistance of a small range is small.
