Repair and analysis methods for multimeters
Patch the essentials
Explore the obstacles should be first outside and then inside, the first easy and then difficult, the whole into zero, focus on breakthroughs. The main points can be roughly divided into the following kinds:
1. feel the law rely on the senses directly on the cause of the obstruction to make a decision, through the surface inspection, can be invented, such as broken wires, de-welding, short-circuiting lap wire, fuse tube broken, burned components, mechanical damage, copper foil on the printed circuit warping and fracture, etc.; can be touched out of the battery, resistors, transistors, integrated blocks of the temperature environment, can be referenced to the circuit diagram to find out the temperature is very high cause. In addition, the hand can also check whether the components are loose, integrated circuit foot tube is firmly inserted, the switch is not cassette; you can hear and smell the sound, odour.
2. The voltage measurement method measures whether the voltage at each critical point is normal, which can quickly identify obstacles. Measure the operating voltage and reference voltage of the A/D converter.
3. short-circuit method in the previously mentioned to check the A/D converter is usually accepted in the short-circuit method, this method in the patch weak and microelectronic instruments used more.
4. Disconnect the suspicious sector from the whole machine or unit circuit to stop open, if the obstacles dissipate, the performance of the obstacles in the disconnected circuit. This method is important for the existence of short-circuit circuit environment.
5. Measurement of components when the obstruction has been reduced to a certain place or a few components, can be held online or offline measurement. When necessary, with a good component replacement, if the obstacle dissipates, the components have been bad.
6. Nuisance method using the human body to feel the voltage as a nuisance signal, inspection of the liquid crystal display of the change in the environment, often used to check the input circuit and the performance of the department is ready.
