The time limiter is an important circuit of the x-ray machine. Once a failure occurs, it may affect the quality of the lighter and the heavyest will damage the x-ray tube. Because there are many types of time limiters, the phenomenon and cause of the fault are different. Taking common failures of electronic time limiters as an example, Fangji Infinite briefly introduces other types of x-ray security inspection equipment to maintain and repair time limiter failures.

1. Common faults and inspection of electronic time limiter
Electronic time limiters include electron tube time limiters, thyristor time limiters, transistor time limiters and integrated circuit time limiters. Here Fangji Infinite Security Machine Manufacturer mainly introduces the common faults and maintenance methods of transistor time limiters.
Transistor failure, whether it is diode, triode, thyristor transistor or single junction transistor, there are two main types. One is breakdown, the other is internal open circuit, which will make the controlled circuit not work properly. When it is suspected that the above fault occurs, it can be determined by observing the working state of the time-limiting relay and further measurement with a multimeter. At this time, a new tube of the same model or replaceable model needs to be replaced.

2. Time limiter inspection procedure Transistor time limiter has a complicated circuit structure. When an abnormality occurs, the electrical parameters should be measured step by step according to the circuit characteristics and working procedures, so as to quickly and accurately detect the fault. The inspection procedure is as follows:

1. Disconnect the high-voltage primary wiring to determine whether the same type of fault occurs at each gear limit.
2. Measure whether the working voltage of each level is normal.
3. Determine whether the rectified DC power supply voltage is normal.
4. Determine whether the AC input voltage of the power supply of the time limiter is normal.
5. Determine whether the last control line, that is, the working state of the high-sensitivity relay is abnormal, whether it cannot work or cannot be released.

3, the failure of highly sensitive relay
1. Contact failure: The contact gap of the high-sensitivity relay is very small, and the gap may change after a long-term operation, resulting in failure such as contact ignition and sticking together. When you observe carefully, you can find that the normally open contact cannot be closed, and the normally closed contact can not be opened. The corresponding control circuit will appear to be unconnected and should be continuously broken. The repair of highly sensitive relays is difficult to ensure that the technical data meets the quality requirements, so once the above failure occurs, new products need to be replaced to avoid greater harm.
2. The coil is open or burned: the coil of the high-sensitivity relay has many turns, the wire diameter is very thin, the internal resistance is large, generally more than 1500 ohms, and the working current is mostly from a few milliamperes to tens of milliamperes, so open circuits or burn. At this time, the relay cannot work, remove it and measure it. If the DC resistance of the coil is infinite, it means an open circuit. If the resistance is small, it is a partial short circuit or burned out.

4, the fault of the RC circuit The RC circuit is the basic circuit of the time limiter, and its main faults are as follows:

1. Capacitor breakdown or open circuit: This will cause the RC circuit to be short-circuited or open circuit, the transistor cannot work normally, the time limiter cannot be limited or non-stop.
2. Change of resistance value: the RC constant is changed, causing the time limit to be extended or shortened, making the time limit inaccurate.
3. Open resistance or burnout: This will also cut off the RC circuit, making charging and discharging impossible, and normal time limit.
4. Capacitor leakage: After the leakage, the charging time between the two ends of the capacitor is extended to the working voltage, and even the working voltage cannot be charged, resulting in inaccurate or non-stop time.