How to Repair a Digital Multimeter
The maintenance and troubleshooting of digital multimeter should be done first from the outside to the inside, from easy to difficult, from breaking down into parts, and focusing on breakthroughs. The methods can be roughly divided into the following:
1. Sensory method
By relying on the senses to directly determine the cause of the fault, through visual inspection, it can be found that such as wire breakage, desoldering, short circuit to grounding, broken fuse tubes, burnt components, mechanical damage, copper foil warping and breakage on printed circuits, etc; You can touch the temperature rise of the battery, resistor, transistor, and integrated block, and refer to the circuit diagram to identify the cause of abnormal temperature rise. In addition, you can also check by hand whether the components are loose, whether the integrated circuit pins are securely inserted, and whether the transfer switch is stuck; Can be heard and smelled for any abnormal sounds or odors.
2. Voltage measurement method
Measuring whether the working voltage of each key point is normal can quickly identify the fault point. For example, measuring the working voltage and reference voltage of the A/D converter.
3. Short circuit method
The short circuit method is generally used in the inspection of A/D converters mentioned earlier, which is more commonly used in repairing weak and micro electrical instruments.
4. Circuit breaking method
Disconnect the suspicious part from the entire machine or unit circuit. If the fault disappears, it indicates that the fault is in the disconnected circuit. This method is mainly suitable for situations where there is a short circuit in the circuit.
5. Measurement element method
When the fault has narrowed down to a certain location or several components, it can be measured online or offline. If necessary, replace with good components. If the fault disappears, it indicates that the component is damaged.
Generally speaking, if a digital multimeter is damaged, it is often caused by our improper operation. For example, when testing a DC circuit, we use the gear of the AC circuit for testing. In fact, this operation has a significant impact on our digital multimeter.
