Ultrasonic flaw detector is a professional detection instrument, it is difficult for professionals to understand the principle. Ultrasonic flaw detector is an instrument used for testing. If its sensitivity is low, then using it for testing is not a bit of a sense of overwhelmingness, so we need to perform sensitivity detection and maintenance on the ultrasonic flaw detector .
(I) Ultrasonic flaw detector to check the transmitting circuit
1. Use a multimeter to measure whether the power supply voltage is too low.
2. Use a multimeter to measure whether the average value of the screen voltage of the thyristor is high or low.
3. Check if capacitor C is leaking.
4. Use a pulse oscilloscope to measure the frequency of the transmitted wave. When checking with a test block, place the probe on the test block so that the reflected wave is on the fluorescent screen, and adjust the iron core of the coil L in the transmitting circuit to make the reflected wave high.
(II) Receiving circuit inspection by ultrasonic flaw detector
1. Measure whether the voltage at all levels is normal.
2. Check the tuning frequency and magnification. There are several methods:
(1) Connect the output of the high-frequency signal generator to the input of the receiving circuit, and connect the voltmeter to the output of the detection circuit. Change the frequency of the high-frequency signal generator and note the value of the voltmeter. When the voltage is large, the frequency should be consistent with the transmission frequency, and the magnification should be noted. If the frequency deviation is too large, the coils of each level need to be adjusted.
(2) Place the probe on the test block so that there are reflected waves on the phosphor screen. Use an oscilloscope to observe whether the waveform of the screen electrodes at each level is larger than the first level. If the waveform of the first level is not large enough, it indicates that there is a problem with that level.
(3) If the amplifier circuit is single-tuned, place the probe on the test block and adjust the cores of the coils at all levels to make the reflected wave high.
3. Check if the tube or transistor is aging.
4. Adjust the operating point.
5. Check whether the tuning coil is broken.