Fault Inspection Procedure and Method of Ultrasonic Detector

The inspection program of ultrasonic detector is from the outside to the inside, from back to front, easy to difficult. The inspection methods include visual inspection, touch inspection, odor inspection, auditory inspection, measurement method, or component replacement method.

Ultrasonic detectors: from the outside to the inside

The so-called from outside to inside means to check the external part of the instrument before checking the internal part. for example, if there is no scanning lines on the fluorescent screen, do not rush to disassemble the ultrasonic detector. Instead, check if the indicator light on the instrument panel is turned on. If it is not lit, check if the fuse is broken.

If the fuse is broken, replace it. If it burns out again after replacing it with a fuse with the specified capacity, check whether the power supply and the power supply conversion socket on the instrument are in the indicated position.

If the power supply is 220 volts and the socket is in the 110-volt position, the converter plug should be swapped to the appropriate position. If the power supply and socket alignment is correct, then the internal components of the equipment should be checked. If the indicator light does not turn on and the fuse is intact, the power cord should be checked for any breaks, the power plug should be inspected for good contact, and the power supply should be tested for electricity. If all of these are normal, then the equipment can be opened up for further inspection.

Ultrasonic detectors: from back to front

The term "from back to front" refers to starting the inspection from the later stages (final stages). For example, if there are no scanning lines on the fluorescent screen and the external components of the flaw detector appear normal, the equipment can be opened up and the time circuit waveform can be observed using an oscilloscope. In this case, start with the later stage (G4) sawtooth wave amplifier.

If a sawtooth wave is present, then the malfunction is likely in the oscilloscope section. If there is no sawtooth wave, then move on to the previous stage, G3 (sawtooth wave circuit), and check if there is a waveform there. If G3 has a waveform, then the malfunction is within the G4 circuit. If G3 also lacks a waveform, then proceed to check the previous stage, G2 (square wave circuit). This process continues iteratively. The inspection procedure is the reverse of the procedure that leads to the operation of the ultrasonic flaw detector.

Ultrasonic detectors: from easy to difficult

This means starting from the easiest place to inspect. For example, if there is no transmitted wave, first touch the "receive" socket on the instrument panel (at this time, the probe should be in a receive/transmit state, and the sensitivity of the amplifier should be set to maximum). If there are no unwanted waves on the fluorescent screen, it can be determined that the amplifier is faulty. If there are unwanted waves, then open up the flaw detector and first check the transmission circuit (if it is a thyristor circuit, adjust the bias voltage potentiometer and observe if a transmitted wave appears on the fluorescent screen). If that is not effective, then check the trigger wave circuit.

Ultrasonic detectors: use your eyes, hands, nose, and ears

Filament breakage can be identified when there are no glowing spots on the glass envelope of the electron tube. If the electron tube has leakage, there will be a yellowish-white deposit on the inner wall of the glass. Burnt resistors will have a black surface, and all of these faults can be observed with the naked eye. If the filament is broken, metal-shell vacuum tubes will not produce heat, which can be determined by touching with your hand.

Faults caused by loose or detached components can be detected by lightly tapping the components with your hand and observing if the waveform changes. Some components, such as resistors, may emit a burnt smell when overloaded, or transformers may cause a short circuit, which can be detected by the nose.

Sometimes, when components such as capacitors are about to break down, they may emit a buzzing sound. When an ultrasonic flaw detector with a converter is in operation, there may be a slight whistling sound, and if this sound is absent, it means the converter is not working. These are all sounds that can be heard.