Digital multimeter, also known as multimeter, multimeter, multimeter or three-meter, is a multi-purpose electronic measuring instrument, generally including ammeter, voltmeter, ohmmeter and other functions. Compared with pointer type multimeters, digital multimeters have the advantages of high precision, fast speed, large input impedance, digital display, accurate readings, strong anti-interference ability, and high degree of measurement automation, and are widely used. But if used improperly, it is easy to cause failure.
Troubleshooting of digital multimeters should generally start with the power supply. The troubleshooting of the digital multimeter can be roughly carried out as follows.
1. Visual inspection.
You can touch by hand whether the temperature rise of batteries, resistors, transistors, and integrated blocks is too high. If the newly installed battery is hot, the circuit may be shorted. In addition, the circuit should also be observed for disconnection, desoldering, mechanical damage, etc.
2. Waveform analysis.
Use an electronic oscilloscope to observe the voltage waveform, amplitude, period (frequency), etc. of each key point of the circuit.
For example, if you check whether the clock oscillator starts, if the oscillator has no output, it means that the internal inverter is damaged, or the external components may be open.
3. Measure the parameters of the components.
For components within the fault range, perform online or offline measurements, and analyze the parameter values. For on-line resistance measurement, the influence of components connected in parallel with it should be considered.
4. Hidden troubleshooting.
Recessive fault refers to the fault that the fault appears and disappears from time to time, and the instrument is good and bad. This kind of fault is more complicated, and the common reasons include solder joints, loose, loose connectors, poor contact of the transfer switch, unstable component performance, and the lead will be broken continuously. In addition, it also includes some external factors. For example, the ambient temperature is too high, the humidity is too high, or there are intermittent strong interference signals nearby, etc.
5. Detect working voltage at all levels.
Detect the working voltage of each point and compare it with the normal value,
First of all, the accuracy of the reference voltage should be ensured. It is best to use a digital multimeter of the same model or similar to measure and compare.
In addition to the above possible reasons, the damage of the digital multimeter may also be caused by the error of the measurement gear. For example, when measuring AC mains, the measurement gear is selected to be placed on the electric block. In this case, once the meter pen touches the mains, it will be instantly. It can cause damage to the internal components of the multimeter. Therefore, be sure to check whether the measurement gear is correct before using the multimeter to measure. After use, set the measurement selection to AC 750V or DC 1000V, so that no matter what parameter is wrongly measured in the next measurement, it will not cause damage to the digital multimeter.
