Multimeter and other instrumentation troubleshooting several methods
1, knocking hand pressure method
Often encountered in the instrument operation of the phenomenon of good and bad, the vast majority of this phenomenon is due to poor contact or false welding. For this situation can be used to knock and hand pressure method. The so-called "knock" is the possible failure of the parts, through a small rubber hammer or other knocks gently hit the plug-in board or components to see whether it will cause errors or shutdown failure. The so-called "hand pressure" is the emergence of faults, turn off the power to the inserted parts and plugs and seats to re-press the hand firmly, and then try to eliminate the fault. If you find a knock on the case is normal, and then knock and not normal, it is best to re-insert all the connectors and try again, if the brain is not successful, we have to think of another way.
2, observation method
The use of sight, smell, touch. At some point, the damaged components will be discoloured, blistering or burnt spots; burnt devices will produce some special smell; short-circuited chip will be hot; with the naked eye can also be observed at the solder or desoldering.
3, exclusion method
The so-called exclusion method is to determine the cause of the failure by unplugging the machine some plug-in boards, devices. When unplugging a plug-in board or device after the instrument returns to normal, it shows that the fault occurs there.
4, replacement method
Requirements for two instruments of the same type or have enough spare parts. Will be a good spare parts and the same components on the fault machine to replace, to see whether the fault is eliminated.
5,Comparison method
Requirements for two instruments of the same type, and one is normal operation. Use this method also have the necessary equipment, for example, multimeter, oscilloscope and so on. According to the nature of the comparison, voltage comparison, waveform comparison, static impedance comparison, output comparison, current comparison. Specific method is: let the faulty instrument and normal instrumentation in the same situation, and then detect some points of the signal and then compare the two sets of signals measured, if there is a difference, it can be concluded that the fault is here. This method requires maintenance personnel have considerable knowledge and skills. Multimeter and other instrumentation troubleshooting ten techniques
6, rise and fall temperature method
Sometimes, the instrument works for a longer period of time, or in the summer working environment at higher temperatures there will be a failure, shutdown check is normal, stop for a period of time and then boot is normal, after a while and then failures. This phenomenon is due to individual IC or component performance is poor, high temperature characteristics of the parameters do not meet the target requirements. In order to find out the cause of the failure, can be used to raise and lower the temperature method. The so-called cooling, that is, when the fault appears, with cotton fibre will be anhydrous alcohol in the possible failure of the parts of the wipe, so that it cools down, and observe whether the fault is eliminated. The so-called warming is artificially high ambient temperature, such as with a soldering iron near the suspect parts (note that the temperature must not be too high so as to damage the normal device) to try to see if the fault appears.
7, riding the shoulder method
Riding shoulder method is also known as the parallel method. A good IC chip on top of the chip to be checked, or good components (resistors and capacitors, diodes, transistors, etc.) and components to be checked in parallel to maintain good contact, if the fault comes from the device internal open circuit or poor contact and other reasons, this method can be excluded.
8, capacitor bypass method
When a circuit produces relatively strange phenomena, such as display confusion, you can use capacitance bypass method to determine the circuit part of the approximate failure. Capacitor across the IC power supply and ground; transistor circuits across the base input or collector output, observe the impact of the failure phenomenon. If the capacitor bypass input is invalid and bypass its output when the fault phenomenon disappears, it is determined that the failure occurs in this circuit.
9, state adjustment method
In general, before the fault is not determined, do not touch the circuit components, especially adjustable devices is more so, such as potentiometers. However, if the measures taken in advance to review the reference (for example, before touching a good position mark or measure the voltage or resistance value, etc.), it is still allowed to touch, if necessary. Perhaps after the change sometimes the fault will be eliminated.
10, isolation method
Fault isolation method does not require the same type of equipment or spare parts for comparison, and ** reliable. According to the fault detection flow chart, divided into a circle to gradually narrow the fault search scope, together with the signal comparison, parts exchange and other methods, generally will soon find the fault is located.
