How to repair the digital multimeter
The maintenance of digital multimeters should be done first from the outside to the inside, from the easy to the difficult. The methods can be roughly divided into the following categories:
1. Sensation
By means of the senses to directly judge the cause of the failure, through the visual inspection, it can be found such as disconnection, de-soldering, short-circuiting, broken fuse tube, burnt components, mechanical damage, and copper foil on the printed circuit. ; You can touch the temperature rise of batteries, resistors, transistors, and integrated blocks, and you can refer to the circuit diagram to find out the reason for the abnormal temperature rise. In addition, you can also check by hand whether the components are loose, whether the integrated circuit pins are firmly inserted, and whether the transfer switch is cassette; you can hear and smell whether there is any abnormal sound or smell.
2. Voltage measurement method
Measure whether the working voltage of each key point is normal, which can quickly find out the fault point. Such as measuring the working voltage of the A/D converter, the reference voltage, etc.
3. Short circuit method
The short-circuit method is generally used in the inspection method of the A/D converter mentioned above. This method is used more in the repair of weak and micro-electrical instruments.
4. Circuit breaking method
Disconnect the suspicious part from the whole machine or unit circuit. If the fault disappears, it means that the fault is in the disconnected circuit. This method is mainly suitable for short circuits in the circuit.
5. Measuring element method
When the fault has been narrowed down to a place or a few components, it can be measured online or offline. If necessary, replace with good components. If the fault disappears, the components are broken.
Generally speaking, if the digital multimeter is damaged, it is often caused by our improper operation. For example, when we are testing a DC circuit, we use the gear of the AC circuit for testing. In fact, such an operation is very damaging to our digital multimeter.
