How to troubleshoot digital multimeter glitches
1. Waveform analysis
Use an electronic oscilloscope to observe the voltage waveform, amplitude, period (frequency), etc. of each key point of the circuit, such as testing whether the clock oscillator is oscillating 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 is open circuit. Observe that the waveform of pin {21} of TSC7106 should be a 50Hz square wave, otherwise the internal 200 frequency divider may be damaged.
2. Measuring component parameters
For online or offline measurements of components within the fault range, parameter values need to be analyzed. When measuring resistance online, the influence of components connected in parallel with it needs to 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 fault is more complex. The 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, there are also some fault problems caused by external factors, such as excessive ambient temperature, excessive humidity or intermittent strong interference signals nearby.
4. Appearance inspection
Touch the battery, resistor, transistor, and integrated block with your hands to see if the temperature rise is too high. If the newly installed battery is hot, it means there is a short circuit in the circuit. In addition, it is also necessary to observe whether the circuit is disconnected, desoldered, mechanically damaged, etc.
5. Detect the working voltage at all levels
To detect the working voltage at each point and compare it with the normal value, 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.
