Troubleshooting methods for hidden faults in digital multimeters
There are many types of digital multimeters with a wide range of applications. However, after all, multimeters are a type of electronic product. Some minor problems may arise during use. Here are some troubleshooting methods.
1. Waveform analysis.
Use an electronic oscilloscope to observe the voltage waveform, amplitude, period (frequency), etc. of each key point in the circuit. For example, test whether the clock oscillator starts to oscillate and whether the oscillation frequency is 40kHz. If the oscillator has no output, it means that the internal inverter of TSC7106 is damaged, or the external component may be open circuit. Observe that the waveform at pin {21} of TSC7106 should be a 50Hz square wave. Otherwise, the internal 200 frequency divider may be damaged.
2. Measure component parameters.
For components within the fault range, conduct online or offline measurements and analyze parameter values. When measuring resistance online, the influence of components connected in parallel with it should be considered.
3. Hidden troubleshooting.
Hidden fault refers to the fault that appears and disappears, and the instrument is good and bad sometimes. This type of failure is relatively complex, and common causes include weak solder joints, loose joints, loose connectors, poor contact of the transfer switch, unstable component performance, and continuous breakage of leads. In addition, it also includes some external factors. Such as the ambient temperature is too high, the humidity is too high or there are intermittent strong interference signals nearby, etc.
4. Appearance inspection.
You can touch the battery, resistor, transistor, and integrated block with your hands to see if the temperature rise is too high. If a newly installed battery becomes hot, the circuit may be short-circuited. In addition, the circuit should also be observed for disconnection, desoldering, mechanical damage, etc.
5. Detect the working voltage at all levels.
To detect the working voltage at each point and compare it with the normal value, you should first ensure the accuracy of the reference voltage. It is best to use a digital multimeter of the same model or a similar one for measurement and comparison.
