Methods for repairing and analysing multimeters
First, patch the essentials
Explore the obstacles should be the first outside after the inside, the first easy after the 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, fuse tube broken, burned components, mechanical damage, printed circuit copper foil warping and fracture, etc.; can be touched out of the battery, resistors, transistors, integrated blocks of the temperature environment, you can refer 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. Measurement of the voltage method 丈量各要害点的事情电压是否正常,可较快找出阻碍点. Such as measuring the A/D converter voltage, reference voltage.
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.
