Typical Troubleshooting Methods for Digital Multimeter Malfunctions
The troubleshooting of digital multimeters usually starts with the power supply. For example, after connecting the power supply, if the LCD cell appears, the first thing to check is whether the voltage of the 9V stacked battery is too low; Is the battery lead disconnected. The search for problems should follow the order of "inside first, then outside, easy first, then difficult". The troubleshooting of a digital multimeter can be roughly carried out as follows.
1, Appearance inspection.
Is the temperature rise of the battery, resistor, transistor, and integrated block that can be touched by hand too high. If the newly installed battery heats up, it indicates that the circuit may be short circuited. In addition, it is necessary to investigate whether the circuit is broken, desoldered, mechanically damaged, etc.
2, Check the voltage of each level of operation.
Check the operating voltage at each point and compare it with the normal value. Firstly, ensure the accuracy of the reference voltage, preferably using a digital multimeter of the same type or similar neighbors for measurement and comparison.
3, Waveform analysis.
Use an electronic oscilloscope to investigate the voltage waveform, fluctuations, period (frequency), etc. of each key point in the circuit. For example, if the clock vibrator is starting to vibrate and the vibration frequency is 40kHz. If the vibrator has no output, it indicates that the TSC7106 internal inverter is damaged, or it may be an open circuit in external components. The waveform observed at pin {21} of TSC7106 should be a 50Hz square wave, otherwise, it may be due to damage to the internal 200 frequency divider.
4, Measure component parameters.
For components within the scope of the problem, online or offline measurements should be taken, and the parameter values should be analyzed. When measuring resistance online, the influence of parallel connected components should be considered.
5, Eliminate hidden problems.
Hidden illness refers to the condition where the problem appears and disappears, and the appearance is sometimes good and sometimes bad. This type of problem is relatively complex, with common elements including solder joints, looseness, loose connectors, poor contact of transfer switches, unstable component function, and continuous breakage of leads. In addition, it also includes some external factors formed. Such as high ambient temperature, high humidity, or intermittent strong interference signals in the vicinity.
