Focus on the detection method of the step-in high-low temperature damp heat test box instrument
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Welcome to our website, the content is provided by Dongguan Haotian Testing Equipment Co., Ltd. The following is a detailed analysis of the inspection method of the walk-in constant temperature and humidity test box instrument, which is explained by Qi Tianxiao.
Method 1: 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 encirclement gradually narrows the fault search range, and then cooperates with the signal comparison and component exchange methods, and generally finds the fault location.
Method 2: Comparison method
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.
Two instruments of the same model 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.
Method three: tapping
It is often encountered when the instrument is running well, which is mostly 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 case is normal, and then knocking is not normal, *Please re-insert all the connectors and try again. If you are not successful, you have to find another way.
Method 4: Observation
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. .
Method 5: State adjustment method
Generally speaking, before the fault is determined, do not touch the components in the circuit, especially the adjustable device, especially the potentiometer. However, if the paperless recorder has previously taken multiple reference measures (for example, making a position mark or measuring a voltage value or a resistance value before touching), it is still allowed to be touched if necessary. Maybe after the change, sometimes the fault will be eliminated. The power supply and ground of the IC; the transistor circuit is connected across the base input or the collector output to observe the effect on the fault phenomenon. If the color paperless recorder's 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.
Method six: 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.
Method 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.
Method eight: lifting temperature method
Sometimes, the instrument works for a long time, or when the working environment temperature is high in summer, it will be faulty. The shutdown check is normal. After stopping for a while, the machine is turned on again and normal. After a while, it fails 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 metal processing network of the cause of the failure, the temperature rise and fall method can be employed.
The so-called cooling, that is, when the fault occurs, use the 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.
Method nine: replacement method
1) Component replacement method: Two instruments of the same type 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.
2) Function replacement method: When the function of a certain part of the faulty machine is lost, because the original spare parts cannot be found at one time, according to the circuit principle of the part, the purchased or self-made electrical parameters have the same function or are replaced by the parts, and the same can be achieved. Repair the purpose of the instrument.
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