Repair and analysis method of multimeter
In the search for obstacles, we should first look at the outside and then the inside, first the easy and then the difficult, break the whole into parts, and break through the key points. Its essentials can roughly be divided into the following categories:
1. The sensory method relies on the senses to directly determine the cause of the failure. Through superficial inspection, it can be found such as disconnection, desoldering, short circuit, broken fuse tube, burned components, mechanical damage, and copper foil on the printed circuit. Warping and fracture, etc.; you can feel 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, by hand, you can also check whether the components are loose, whether the integrated circuit pins are firmly inserted, and whether the switch is stuck; you can hear and smell whether there are abnormal sounds and odors.
2. Voltage measurement method: measure whether the working voltage of each key point is normal, and find out the fault point quickly. 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 inspection methods of A/D converters mentioned above. This method is often used when repairing weak and micro-electric instruments.
4. Open circuit method: Disconnect the suspicious part from the complete machine or unit circuit. If the fault disappears, it means that the fault is in the disconnected circuit. This method is mainly suitable for the environment where there is a short circuit in the circuit.
5. Component measurement method When the fault has been reduced to a certain place or several components, it can be measured online or offline. If necessary, replace with good components, if the failure disappears, it means the components are broken.
6. Interference method Use the human body's sensed voltage as the interference signal to observe the change of the liquid crystal display. It is often used to check whether the input circuit and the display part are complete.
