Troubleshooting method of digital multimeter
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 whether the clock oscillator starts to vibrate and whether the oscillation frequency is 40kHz.
If the oscillator has no output, it means that the internal inverter of the TSC7106 is damaged, or the external components are open. Observe that the waveform of the {21} foot of TSC7106 should be a 50Hz square wave, otherwise the internal 200 frequency divider may be damaged.
2. Measuring component parameters
On-line or off-line measurement of components within the fault range requires analysis of parameter values. When measuring resistance online, the influence of the components connected in parallel with it needs to be considered.
3. Hidden troubleshooting
Recessive faults refer to the faults that appear and disappear from time to time, and the faults of the instrument are good and bad. This kind of fault is more complicated, and the causes of the fault 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 faults caused by some external factors, such as high ambient temperature, high humidity or intermittent strong interference signals nearby.
4. Visual inspection
Touch whether the temperature rise of the battery, resistor, transistor, and integrated block is too high. If the newly installed battery heats up, it means that the circuit is short-circuited. In addition, it is also necessary to observe whether the circuit is disconnected, desoldered, mechanical damage, etc.
5. Detect working voltage at all levels
Detect the working voltage of 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 similar to measure and compare.
The above is the troubleshooting method of the five types of small faults of the digital multimeter, I hope it will be helpful to everyone.
