How to repair and troubleshoot digital multimeters
Digital instrumentation has a high degree of sensitivity and accuracy, and its application in almost all enterprises. However, due to its failure to appear as a multi-factor, and encountered problems with the randomness of the large, there is not much regularity to follow, the repair is more difficult. Therefore, I will work for many years in the actual accumulation of some of the repair experience collated for colleagues engaged in this profession for reference. Capacitive voltage divider high voltage measurement system for pulse high voltage, lightning high voltage, high frequency high voltage measurement, is instead of high voltage static voltmeter shou choice.
Repair method.
Looking for faults should be the first outside after the inside, the first easy after the difficult, the whole into zero, focus on breakthroughs. The method can be broadly divided into the following categories:
Feeling method By virtue of the senses directly to the cause of the failure to make a judgement, through the appearance of the inspection, can be found, such as broken wires, de-welding, short-circuiting lap wire, fuse tube broken, burnt components, mechanical damage, copper foil on the printed circuit warping and fracture, etc.; you can touch out of the battery, resistors, transistors, integrated blocks of the temperature rise, you can refer to the circuit diagrams to find out the reasons for the temperature rise abnormalities. In addition, the hand can also check whether the components are loose, whether the IC foot tube is inserted firmly, whether the changeover switch is cassette; you can hear and smell whether there is a strange sound, odour.
2. Measurement of voltage method Measurement of the key points of the operating voltage is normal, you can quickly find out the point of failure. Such as measuring the working voltage of the A/D converter, reference voltage.
3. short-circuit method in the previously mentioned methods of checking the A/D converter are generally used in the short-circuit method, this method is used in the repair of weak and microelectronic instruments.
4. Disconnect the suspicious part from the whole machine or unit circuit disconnect, if the fault disappears, said the fault in the disconnected circuit. This method is mainly suitable for the existence of short-circuit circuit.
5. Measurement of components When the fault has been narrowed down to a certain place or a few components, it can be measured online or offline. If necessary, replace the components with good ones, if the fault disappears, the components are bad.
6. Interference method The use of human induced voltage as an interference signal, observe the changes in the liquid crystal display, often used to check the input circuit and the display part is intact.
