6 ways to repair your digital multimeter
Digital meters have high sensitivity and accuracy and are used in almost every enterprise. However, because its failures occur due to multiple factors, and problems encountered are highly random, there are not many rules to follow, and repairs are difficult. Therefore, I have compiled some repair experience accumulated in many years of work for reference by colleagues in this profession.
Repair method
When looking for faults, you should first look for the outside and then the inside, first the easy and then the difficult, break it into parts, and focus on breakthroughs. The methods can be roughly divided into the following categories:
1. The sensory method relies on the senses to directly judge the cause of the fault. Through visual inspection, it can be found such as broken wires, desoldering, short circuits, broken fuse tubes, burned components, mechanical damage, and warped copper foil on printed circuits. rise and break, etc.; you can touch the temperature rise of batteries, resistors, transistors, and integrated blocks, and refer to the circuit diagram to find out the cause of abnormal temperature rise. In addition, you can also use your hands to check whether the components are loose, whether the integrated circuit pins are firmly inserted, and whether the transfer switch is stuck; you can hear and smell whether there are any strange sounds and smells.
2. Voltage measurement method: Measuring whether the working voltage of each key point is normal can quickly find the fault point. Such as 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 methods of checking A/D converters mentioned above. This method is often used when repairing weak current 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 situations where there is a short circuit in the circuit.
5. Component measurement method: When the fault has been reduced to a certain component or several components, it can be measured online or offline. If necessary, replace it with a good component. If the fault disappears, it means the component is bad.
6. Interference method: Use the induced voltage of the human body as an interference signal to observe the changes in the liquid crystal display. It is often used to check whether the input circuit and display part are intact.
