Instrumentation circuit maintenance has always been an indispensable part of electronics companies. Because only through it can the original unqualified products finally leave the factory. However, repairing instrumentation is also the most complex part of an electronics company. Because it not only uses a lot of electronic expertise, but also requires a wealth of field experience.

1. Tapping pressure method

It is often encountered that the instrument is running at a good or bad time. Most of this phenomenon is caused by poor contact or solder joints. For this case, tapping and hand pressing can be used.

The so-called "knocking" is to gently knock the board or part through a small rubber hammer or other tapping object to see if it will cause an error or a downtime. The so-called "hand pressure" is when the fault occurs, after the power is turned off, the inserted components and the plug and the seat are again pressed by hand, and then the power is turned on to try to eliminate the fault. If you find that the casing is normal and the knocking is not normal, it is best to re-insert all the joints and try again. If the brain is unsuccessful, you have to find another way.

2, observation method

Use vision, smell, and touch. In some cases, damaged components will change color, blister or burnt spots; burnt devices will produce some special odor; short-circuited chips will be hot; visible or desoldered parts can also be observed with the naked eye. .

3. Exclusion method

The so-called elimination method is a method for judging the cause of the failure by plugging in some boards and devices inside the machine. When the instrument returns to normal after removing a board or device, the fault has occurred there.

4, replacement method

Two instruments of the same model are required or there are enough spare parts. Replace a good spare with the same component on the faulty machine to see if the fault is eliminated.

5, comparison method

Two instruments of the same type are required, and one is in normal operation. Use this method to have the necessary equipment, such as a multimeter, oscilloscope, etc. According to the nature of the comparison, voltage comparison, waveform comparison, static impedance comparison, output comparison, current comparison, etc.

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

6, lifting temperature method

Sometimes, the instrument works for a long time, or when the working temperature in the summer is high, the fault will occur. The shutdown check is normal. After stopping for a while, the power is turned on again and normal. After a while, the fault occurs again. This phenomenon is caused by the poor performance of individual ICs or components, and the high-temperature characteristic parameters fail to meet the requirements of the index. In order to find out the cause of the malfunction, the temperature rise and fall method can be employed

The so-called cooling, that is, when the fault occurs, use cotton fiber to wipe the anhydrous alcohol in the part that may be faulty, to cool it, and observe whether the fault is eliminated. The so-called heating is artificially raising the ambient temperature, such as using a soldering iron to close the suspected part (be careful not to raise the temperature too high to damage the normal device) to see if the fault occurs.

7, riding the shoulder method

The shoulder riding method is also called parallel method. Place a good IC chip on the chip to be inspected, or connect good components (resistance capacitors, diodes, transistors, etc.) in parallel with the components to be inspected, and keep in good contact. If the fault is caused by an open circuit inside the device or This method can be used to eliminate the cause of poor contact.

8, capacitor bypass method

When a circuit produces a strange phenomenon, such as a display disorder, the capacitor bypass method can be used to determine the portion of the circuit that is likely to fail. Connect the capacitor across the power supply and ground of the IC; connect the transistor circuit across the base input or collector output to observe the effect on the fault. If the capacitor bypass input is inactive and the fault disappears when bypassing its output, it is determined that the fault is present in this stage of the circuit.

9, state adjustment method

In general, do not touch the components in the circuit before the fault is determined, especially for adjustable devices, such as potentiometers. However, if a reference is taken in advance (for example, position mark or measured voltage value or resistance value before untouched), it is allowed to be touched if necessary. Maybe after the change, sometimes the fault will be eliminated.

10. Isolation method

Fault isolation does not require the same type of equipment or spare parts for comparison and is safe and reliable. According to the fault detection flow chart, the segmentation and enveloping gradually narrows the fault search range, and then cooperates with the signal comparison and component exchange methods, and generally finds the fault of the instrumentation.

Disposable Gloves

Disposable gloves are available in latex and synthetic materials, in sterile and non-sterile forms and with and without powder. Sterile disposable gloves should be worn during invasive procedures and when the hands are in contact with wounds. Non-sterile disposable gloves are recommended when the hands are in contact with blood and other body fluids and for indirect contact with wounds.