Elimination method of hidden fault of digital multimeter
There are many kinds of digital multimeters, and their applications are also very wide. However, after all, multimeters belong to one of electronic products, and there may be some minor problems in the process of use. Here are some tips for troubleshooting.
1. Waveform analysis.
Observe the voltage waveform, amplitude, period (frequency) of each key point of the circuit with an electronic oscilloscope. For example, if the clock oscillator starts to vibrate or not, the oscillation frequency is 40kHz. If the oscillator has no output, it means that the internal inverter of TSC7106 is damaged, or the external components may be open. Observe that the waveform of the {21st} pin of TSC7106 should be a 50Hz square wave, otherwise, it may be the damage of the internal 200 frequency divider.
2. Measure the component parameters.
For the components within the fault range, online measurement or offline measurement shall be conducted, and the parameter values shall be analyzed. When measuring the resistance online, the influence of the components connected in parallel should be considered.
3. Hidden troubleshooting.
Implicit fault refers to the fault when the fault is hidden, and the instrument is good or bad. This kind of fault is complicated, and the common reasons include virtual welding of solder joints, loosening of connectors, poor contact of transfer switch, unstable performance of components, and continuous breakage of leads. 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.
4. Appearance inspection.
You can touch whether the temperature rise of batteries, resistors, transistors and integrated blocks is too high by hand. If the newly installed battery is hot, the circuit may be short-circuited. In addition, you should also observe whether the circuit is broken, soldered, mechanically damaged, etc.
5, detect the working voltage at all levels.
To detect the working voltage of each point and compare it with the normal value, the accuracy of the reference voltage should be ensured first, and it is best to use a digital multimeter of the same model or similar to measure and compare it.
