Troubleshooting Guide for Multimeters
A digital multimeter, also known as a multimeter, multimeter, multimeter, or multimeter, is a multi-purpose electronic measuring instrument that generally includes functions such as an ammeter, voltmeter, ohmmeter, etc. Compared with pointer multimeters, digital multimeters are widely used due to their high accuracy, fast speed, large input impedance, digital display, accurate readings, strong anti-interference ability, and high degree of measurement automation. But if used improperly, it can easily cause malfunctions.
Troubleshooting a digital multimeter generally starts with the power supply. The troubleshooting of a digital multimeter can be roughly carried out as follows.
1. Appearance inspection.
You can touch the temperature rise of the battery, resistor, transistor, and integrated block with your hand to check if it is too high. If the newly installed battery heats up, it indicates that the circuit may be short circuited. In addition, it is necessary to observe whether the circuit is broken, desoldered, mechanically damaged, etc.
2. Waveform analysis.
Observe the voltage waveform, amplitude, period (frequency), etc. of each key point in the circuit using an electronic oscilloscope. For example, if the clock oscillator is tested for oscillation, and there is no output from the oscillator, it indicates that the internal inverter is damaged, or it may be an open circuit in external components.
3. Measure component parameters.
For components within the fault range, online or offline measurements should be conducted, and parameter values should be analyzed. When measuring resistance online, the influence of components connected in parallel should be considered.
4. Hidden troubleshooting.
Hidden faults refer to faults that appear and disappear intermittently, with the instrument panel fluctuating between good and bad. This type of fault is quite complex, and common causes include virtual soldering of solder joints, loosening, loose connectors, poor contact of transfer switches, unstable component performance, and continuous breakage of leads. In addition, it also includes factors caused by external factors. Such as high ambient temperature, high humidity, or intermittent strong interference signals nearby.
5. Detect the working voltage at all levels.
To detect the working voltage at each point and compare it with the normal value, the accuracy of the reference voltage should be ensured first. It is best to use a digital multimeter of the same or similar model for measurement and comparison.
In addition to the possible reasons mentioned above, the damage to the digital multimeter may also be caused by an error in the measurement gear. For example, when measuring AC mains power, if the measurement gear is selected to be in the resistance gear, once the probe contacts the mains power, it can instantly cause damage to the internal components of the multimeter. Therefore, before using a multimeter for measurement, it is necessary to check whether the measurement gear is correct. After use, place the measurement selection at AC 750V or DC 1000V, so that no matter what parameter is mistakenly measured in the next measurement, it will not cause damage to the digital multimeter.
