Ten techniques for troubleshooting multimeters and other instrumentation
1, knocking hand pressure method
Ø Often encountered when the instrument is running good and bad phenomenon, the vast majority of this phenomenon is due to contact ** or caused by false welding. For this situation can be used to knock and hand pressure method. The so-called "knocking" is the possible failure of the parts, through a small rubber hammer or other knocking objects gently hit the plug-in board or parts, 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, * good first all the connectors re-inserted firmly and then try, if the brain is not successful, we have to think of another way.
2,Observation method
Ø The use of vision, smell, sense of touch. At some point, the damaged components will be discoloured, blistering or burnt spots; burnt devices will produce some special smell; short-circuited chips will be hot; with the naked eye can also be observed at the virtual welding or desoldering.
3,Exclusion method
Ø The so-called exclusion method is to determine the cause of the failure by unplugging some of the plug-in boards and devices in the machine. When unplugging a plug-in board or device after the instrument returns to normal, it shows that the fault occurs there.
4,Replacement method
Ø Require two instruments of the same model or have enough spare parts. Replace a good spare part with the same component on the faulty machine to see whether the fault is eliminated.
5,Comparison method
Ø Requirements for two sets of the same type of instrument, 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,Lifting and cooling method
Ø Sometimes, the instrument works for a long time, or in the summer working environment when the temperature is high, there will be a failure, shutdown check is normal, stop for a period of time and then power on is normal, after a while there is a failure. 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
Ø Riding the shoulder method is also known as the parallel connection method. A good IC chip in the chip to be checked on top of the chip, or good components (resistors and capacitors, diodes, transistors, etc.) and components to be checked in parallel, to maintain good contact, if the failure comes from the device inside the open circuit or contact ** and other reasons, the use of this method can be ruled out.
8, capacitor bypass method
Ø When a circuit produces strange phenomena, such as display confusion, you can use capacitance bypass method to determine the approximate failure of the circuit part. Capacitor across the IC power supply and ground; transistor circuit 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
Ø 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 you take reference measures in advance (for example, before touching a good position mark or measure the voltage or resistance value, etc.), it is still allowed to touch when necessary. Perhaps after the change sometimes the fault will be eliminated.
10,Isolation method
Ø Fault isolation method does not require the same type of equipment or spare parts for comparison, but also safe and reliable. According to the fault detection flowchart, the division of the enclosure gradually narrow the scope of the fault search, coupled with the signal comparison, parts exchange and other methods, generally will soon find the fault of the location.
