Photocoupler

Some methods of instrumentation fault diagnosis

Beijing Zhongyi Yusheng Technology Co., Ltd.

1. Tapping pressure method

It is often encountered when the instrument is running well, which is mostly caused by poor contact or solder joints. For this case, tapping and hand pressing can be used.

The so-called "knocking" is to gently knock the board or part through a small rubber hammer or other tapping object to see if it will cause an error or a downtime. The so-called "hand pressure" is when the fault occurs, after the power is turned off, the inserted components and the plug and the seat are again pressed by hand, and then the power is turned on to try to eliminate the fault. If you find that the casing is normal and the knocking is not normal, it is best to re-insert all the joints and try again. If the brain is unsuccessful, you have to find another way.

2, observation method

Use vision, smell, and touch. In some cases, damaged components will change color, blister or burnt spots; burnt devices will produce some special odor; short-circuited chips will be hot; visible or desoldered parts can also be observed with the naked eye. .

3. Exclusion method

The so-called elimination method is a method for judging the cause of the failure by plugging in some boards and devices inside the machine. When the instrument returns to normal after removing a board or device, the fault has occurred there.

4, replacement method

Two instruments of the same model are required or there are enough spare parts. Replace a good spare with the same component on the faulty machine to see if the fault is eliminated.

5, comparison method

Two instruments of the same model are required and one is in normal operation. Use this method to have the necessary equipment, such as a multimeter, oscilloscope, etc. According to the nature of the comparison, voltage comparison, waveform comparison, static impedance comparison, output comparison, current comparison, etc.

The specific method is: let the faulty meter and the normal meter run under the same conditions, and then detect the signals of some points and then compare the two groups of signals measured. If there are differences, it can be concluded that the fault is here. This method requires the maintenance personnel to have considerable knowledge and skills.

6, lifting temperature method

Sometimes, the instrument works for a long time, or when the working environment temperature is high in summer, it will be faulty. The shutdown check is normal. After stopping for a while, the power is turned on again and normal. After a while, the fault occurs again. This phenomenon is caused by the poor performance of individual ICs or components, and the high-temperature characteristic parameters fail to meet the requirements of the index. In order to find out the cause of the fault, the temperature rise and fall method

The so-called cooling, that is, when the fault occurs, use cotton fiber to wipe the anhydrous alcohol in the part that may be faulty, to cool it, and observe whether the fault is eliminated. The so-called heating is artificially raising the ambient temperature, such as using a soldering iron to close the suspected part (be careful not to raise the temperature too high to damage the normal device) to see if the fault occurs.

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Beijing Zhongyi Yusheng Technology Co., Ltd.