Troubleshooting the most common faults of the digital multimeter
A digital multimeter is a portable instrument with high sensitivity and intuitive readings that can be used to measure various items such as current, voltage, resistance, etc. In addition, it can also judge the performance of components such as transistors and diodes, which are commonly used tools in wireless work. But due to its fragility, it often causes damage due to improper use. As an instrument, it is inevitable to encounter some malfunctions during use. Below are several common troubleshooting methods described in detail.
1. No display when turned on.
Cause measures: Check if the fuse, power supply circuit, and display are damaged, and if the battery voltage is too low.
2. Abnormal DC voltage range
Reason and measure: If the A/D converter+IN and - IN are short circuited and displayed as zero, it indicates that the fault lies in the DC voltage input part before the A/D converter. The DC voltage level is normal, but there are abnormalities in the AC current or AC voltage level, usually due to damage to the I/V converter or AC/DC converter.
3. Ohm gear abnormal
Reason and measure: It may be caused by an open circuit of the thermistor.
4. Abnormal capacitor configuration
Reason and measures: Mainly due to damage to the ICM7556 integrated block.
5. During measurement, the deviation of the ohm range indicator value is too large
Reason measures: Generally, it is due to poor contact of the conversion switch, which can be wiped with anhydrous alcohol.
6. Excessive deviation in AC voltage range
Reason and measure: The calibration potentiometer in the AC/DC conversion circuit can be adjusted. The deviation of each gear is too large, and the reference voltage value should be adjusted (normal value of 100mV).
