Troubleshooting Methods for Hidden Faults of Digital Multimeter

There are many types of digital multimeters and their applications are also very wide. However, after all, multimeter is a kind of electronic product, so there may be some minor problems during use. Here are some tips for troubleshooting.

1. 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 want to measure 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 may be open. The waveform of the {21}th pin of TSC7106 should be a 50Hz square wave, otherwise, it may be that the internal 200 divider is damaged.

2. Measure component parameters.

For components within the fault range, online or offline measurements should be performed and parameter values ​​should be analyzed. When measuring resistance online, the influence of components connected in parallel should be considered.

3. Troubleshoot hidden faults.

Hidden faults refer to faults that appear and disappear from time to time, and the instrument works sometimes and sometimes not. This type of fault is relatively complex, and common causes include solder joints, loose solder joints, loose connectors, poor contact of transfer switches, unstable component performance, and lead wires that are about to break. In addition, some external factors are also involved, such as excessively high ambient temperature, excessive humidity, or intermittent strong interference signals nearby.

4. Appearance inspection.

You can use your hands to touch the temperature rise of batteries, resistors, transistors, and integrated circuits to see if they are too high. If a newly installed battery is hot, it means the circuit may be short-circuited. In addition, you should also observe whether the circuit is broken, desoldering, or mechanically damaged.

5. Check the working voltage at each level.

Detect the working voltage at each point and compare it with the normal value. First, the accuracy of the reference voltage should be ensured. It is best to use a digital multimeter of the same or similar model for measurement and comparison.