Ten Practical Tips for Using a Digital 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 "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.
7. When measuring resistance, every gear shift requires
Zero adjustment. The value at the geometric center of the resistance scale of a multimeter multiplied by the power blocking ratio is the median resistance of that gear, which is equal to the internal resistance of the multimeter in that gear. The common center scale values are 8. 10. 12. 13. 16. 20. 24. 25-30. There are various types such as 60-75. The resistance scale is non-linear, so when using it, choose the appropriate gear so that the pointer points as close to the center as possible, usually at 0. The reading is accurate within the range of 1Ro-10Ro (Ro - median resistance), and there is a significant error outside of this range. For example, the center scale value of the MF10 multimeter is 13, and in the Rx10 kiloohm range Ro
=At 130 kWh, this gear is suitable for testing at 13 kWh -1. A 3 megaohm resistor.
8. When measuring resistance with a multimeter, the red probe is connected to the negative terminal of the battery inside the meter, and the black probe is connected to the positive terminal of the battery inside the meter. The purpose of doing this is to ensure that the multimeter can measure voltage, current, or resistance uniformly with the red probe in and the black probe out, and the probe can deflect in the normal direction without reversing. Remember to connect the red probe to the negative terminal of the battery and the black probe to the positive terminal, which is useful for checking polarized components such as transistors, diodes, and electrolytic capacitors.
9. When checking large capacity capacitors with resistance gear, the capacitors should be discharged first to prevent residual voltage from damaging the multimeter. One end of the resistor on the test circuit should be disconnected to avoid the influence of other resistors on the circuit. It is prohibited to measure the resistance of a working circuit using a resistor.
10. After the measurement is completed, the range switch should be turned to the voltage high gear to prevent accidental burning of the meter during the next use. If there is a "black dot" or "OFF" mark, the switch should be turned to this position to short-circuit the measuring mechanism.
