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Digital multimeter, also known as multimeter, Multimeter, multi-purpose electricity meter or three purpose electricity meter, is a multi-purpose electronic measuring instrument, generally including ammeter, Voltmeter, Ohmmeter and other functions. Compared with pointer type multimeter, digital multimeter has the advantages of high accuracy, fast speed, large input impedance, accurate digital display and reading, strong anti-interference ability, and high degree of measurement automation, and is widely used. But if used improperly, it can easily cause malfunctions.

Troubleshooting a digital multimeter should generally start with the power supply. The troubleshooting of a digital multimeter can be roughly carried out as follows.

1. Visual inspection.

You can touch the temperature rise of the battery, resistor, transistor, and integrated block with your hand to see if it is too high. If the newly installed battery heats up, it indicates that the circuit may be short circuited. In addition, it is also necessary to observe whether the circuit is disconnected, desoldered, mechanically damaged, etc.

2. Waveform analysis.

Use an electronic oscilloscope to observe the voltage waveform, amplitude, period (frequency), etc. of each key point in the circuit. For example, if the clock oscillator is on, if there is no output from the oscillator, it indicates that the internal inverter is damaged, or it may be due to an open circuit in external components.

3. Measure component parameters.

For components within the fault range, parameter values should be analyzed for online or offline measurements. When measuring resistance online, the influence of components in parallel with it should be considered.

4. Hidden troubleshooting.

Implicit faults refer to faults that appear and disappear from time to time, and the instrument is sometimes good or bad. This type of fault is quite complex, and common reasons include solder joints being loose, loose connectors, poor contact of the transfer switch, unstable component performance, and continuous disconnection of the leads. In addition, it also includes factors caused by external factors. If the ambient temperature is too high, the humidity is too high, or there are intermittent strong interference signals nearby, etc.

5. Detect the working voltage at all levels.

Detect the working voltage at each point and compare it with the normal value. Firstly, ensure the accuracy of the reference voltage, preferably using a digital multimeter of the same model or similar for measurement and comparison.

In addition to ruling out the above possible reasons, the damage to the digital multimeter may also be caused by an error in the measurement gear. For example, when measuring AC mains power, the measurement gear is selected to be in the resistance gear. In this case, once the probe contacts the mains power, it can instantly cause damage to the internal components of the multimeter. Therefore, before using a multimeter for measurement, it is necessary to check whether the measurement gear is correct. After use, place the measurement at either AC 750V or DC 1000V, so that no matter what parameter is mistakenly measured in the next measurement, it will not cause damage to the digital multimeter.