Schneider instrumentation fault diagnosis method

1. Percussion hand pressure method

When we use the instrument, we often encounter the phenomenon that the instrument is running well and badly, and most of this phenomenon is caused by poor contact or virtual welding. In this case, percussion and hand pressure can be used.

The so-called "tapping" is to gently hit the plug-in board or part with a small rubber tip or other percussion object on the part that may be defective to see if it will cause mistakes or downtime. The so-called "hand pressure" is that when the problem is presented, after turning off the power supply, the plugged parts and plugs and seats are pressed by hand from the beginning, and then the machine is turned on to see if the problem will be eliminated. If you find that hitting the casing is normal, and then hitting it is not normal, it is better to reinsert all the joints firmly and then try, if it is not successful, you have to find another way.

Schneider instrumentation fault diagnosis method

Schneider instrumentation fault diagnosis method

2. Observation

Use sight, smell, touch. At certain times, damaged components may become discolored, blistered, or burnt mottled; Burnt equipment will have some special odors; Chips that are short-circuited will get hot; False soldering or desoldering can also be seen with the naked eye.

3. Sweeping method

The so-called cleaning method is a method to identify the cause of the problem through some plug-in boards and equipment in the plug-in machine. When a plug-in board or device is removed and the appearance returns to normal, it indicates that something is wrong there.

4. Substitution method

Two instruments of the same type or sufficient spare parts are required. Replace a good spare part with the same equipment on the faulty machine to see if the fault is eliminated.

5. Comparative method

It is required to have two units of the same type and one of them to be in normal operation. The use of this method also requires the necessary equipment, such as multimeters, oscilloscopes, 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 defective appearance and the normal appearance operate under the same conditions, and then detect the signals at some points and then compare the two sets of signals measured, if there is a difference, you can conclude that the fault is here. This approach requires considerable common sense and skill on the part of maintenance personnel.

6. Temperature rise and fall method

Sometimes, the appearance of the operation for a long time, or in the summer when the temperature of the operating environment is high, it will show problems, shut down to check normal, stop for a period of time and then turn on the machine is normal, and after a moment again, there will be problems. This phenomenon is caused by the poor function of a single IC or element, and the high-temperature characteristic parameters do not meet the requirements of the index. In order to find out the cause of the problem, the temperature rise and fall method can be used.

The so-called cooling is to wipe the anhydrous alcohol with cotton fiber on the part that may be defective when the problem appears, so as to cool it down and observe whether the problem is eliminated. The so-called heating is to artificially raise the ambient temperature, for example, use an electric soldering iron near the suspicious part (be careful not to raise the temperature too high and damage the normal equipment) to see if the problem appears.

7. Shoulder riding method

The shoulder riding method is also known as the parallel method. Put a good IC chip on the chip to be viewed, maybe the good components (resistors, capacitors, diodes, transistors, etc.) and the components to be viewed in parallel, insist on outstanding contact, if the fault comes from the internal open circuit of the equipment or poor contact, etc., this method can be used to sweep away.

8. Capacitor bypass method

When a strange phenomenon occurs in a certain circuit, such as a display disorder, it is possible to use the capacitive bypass method to determine the part of the circuit that is out of order. Briddling capacitors over the IC's power supply and ground; The transistor circuit is bridged at the base input or collector output to observe the effect on the fault phenomenon. If the capacitor bypasses the input and disappears when bypassing its output, it is determined that the fault is present in this stage of the circuit.

9. Situation adjustment method

Generally speaking, before the fault is determined, do not casually affect the components in the circuit, especially adjustable equipment, such as potentiometers. However, if a cross-reference measure is adopted in advance (e.g., position marking or voltage or resistance value is measured before it is pulled), it is still agreed if necessary. Maybe after the change, sometimes the problem will be eliminated.

10. Isolation method

Fault isolation does not require comparisons of the same type of equipment or spare parts, and is safe and reliable. According to the fault detection flow chart, the division and enclosure gradually reduce the scale of fault finding, and then cooperate with signal comparison, component exchange and other methods, generally the fault will be found quickly.

Schneider instrumentation fault diagnosis method

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