Brief Analysis of Instrument Testing Methods

The maintenance of instruments and meters is an integral part of the electronics market. Only by relying on good testing technology can instrument and meter companies ensure that those unqualified products can finally enter the market as qualified ones. The technical staff of instrument and meter companies must have a good foundation of electronic professional knowledge and rich on-site experience.

1. Tap hand pressure method

It is common to encounter the phenomenon that the instrument works well and sometimes not. This phenomenon is mostly caused by poor contact or cold soldering. For this situation, you can use the knocking and hand pressure method.

The so-called "knocking" is to gently knock the plug-in board or component with a small rubber hammer or other knocking objects on the part that may cause the fault, to see if it will cause an error or shutdown fault. The so-called "hand pressing" is to turn off the power and press the plugged components, plugs and sockets firmly by hand when a fault occurs, and then turn on the machine to see if the fault can be eliminated. If it is found that it is normal to knock the case once, but it is not normal when knocked again, it is best to re-insert all the connectors and try again. If the brain-wracking method does not work, you have to find another way.

2. Observation method

Use your sense of sight, smell, and touch. Sometimes, damaged components will change color, bubble, or have burnt spots; burnt devices will produce some special smells; short-circuited chips will get hot; and cold or loose solder joints can be observed with the naked eye.

3. Elimination method

The so-called elimination method is to determine the cause of the fault by plugging in and out some plug-in boards and components in the machine. When the instrument returns to normal after a plug-in board or component is removed, it means that the fault occurred there.

4. Replacement method

It is required to have two instruments of the same model or sufficient spare parts. Replace a good spare part with the same component on the faulty machine to see if the fault is eliminated.

5. Contrast method

It requires two instruments of the same model, and one of them is in normal operation. This method also requires necessary equipment, such as a multimeter, oscilloscope, etc. According to the nature of the comparison, there are voltage comparison, waveform comparison, static impedance comparison, output result comparison, current comparison, etc.

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