Several methods for fault diagnosis of multimeter and other instruments
1. Tapping hand pressure method
It is common to encounter the phenomenon of good and bad operation of instruments, which is mostly caused by contact safety or virtual soldering. For this situation, tapping and hand pressure methods can be used. The so-called "tapping" refers to gently tapping the plug-in board or component with a small rubber mallet or other tapping object on the possible faulty part to see if it will cause errors or shutdown faults. The so-called 'manual pressure' refers to the process of turning off the power and then manually pressing the plugged components, plugs, and sockets back firmly when a fault occurs, and then turning on the machine to see if it can eliminate the fault. If it is found that knocking the casing once is normal, and then knocking it again is not normal, it is best to first re plug all the connectors and try again. If it is troublesome and unsuccessful, we have to find another way.
2. Observation method
Utilize visual, olfactory, and tactile senses. Sometimes, damaged components may discolor, bubble, or show burnt spots; Burned components will produce some special odors; Short circuited chips will heat up; Virtual welding or detachment can also be observed with the naked eye.
3. Exclusion method
The so-called elimination method is a method of determining the cause of faults by plugging and unplugging some plug-in boards and components inside the machine. When the instrument returns to normal after removing a certain plug-in board or component, it indicates that the fault occurred there.
4. Substitution method
Require two instruments of the same model or sufficient spare parts. Replace a good spare part with the same component on the faulty machine and see if the fault is eliminated.
5. Comparison method
Two instruments of the same model are required, and one of them is operating normally. Necessary equipment such as multimeters and oscilloscopes are also required to use this method. According to the nature of comparison, there are voltage comparison, waveform comparison, static impedance comparison, output result comparison, current comparison, etc. The specific method is to operate the faulty instrument and the normal instrument under the same conditions, and then detect the signals of some points and compare the two sets of signals measured. If there are differences, it can be concluded that the fault lies here. This method requires maintenance personnel to have considerable knowledge and skills. Ten methods for diagnosing faults in multimeters and other instruments
6. Heating and cooling method
Sometimes, when the instrument works for a long time or when the working environment temperature is high in summer, it will malfunction. After shutting down and checking, it will work normally. After stopping for a period of time and then restarting, it will work normally again, and then the malfunction will occur again after a while. This phenomenon is caused by poor performance of individual ICs or components, and the high-temperature characteristic parameters cannot meet the requirements of the indicators. To identify the cause of the malfunction, the temperature rise and fall method can be used. The so-called cooling refers to using cotton fibers to wipe anhydrous alcohol on the possible faulty area when a malfunction occurs, to cool it down and observe whether the malfunction is eliminated. The so-called temperature rise refers to artificially raising the ambient temperature, such as placing an electric soldering iron close to the suspicious area (be careful not to raise the temperature too high and damage normal components) to see if a fault occurs.
