What are the factors that affect the measurement of the ultrasonic thickness gauge? (1)

(1) The surface roughness of the workpiece is too large, which is resulting in the poor coupling between the probe and the contact surface, low reflection echo, and even failure to receive the echo signal. For surface rust, in-service equipment, pipes, etc., anodizing coating thickness gauges have extremely poor coupling effects, can be treated by sand, grinding, and frustration to reduce the roughness, and the oxide and paint layers can be removed to expose the metallic luster. A good coupling effect can be achieved by the coupling agent with the test object.

(2) The radius of curvature of the workpiece is too small, especially when the small diameter tube is thick, because the surface of the common probe is flat, the contact with the curved surface is point contact or line contact, and the sound intensity transmission is low (coupling is not good). A small diameter probe (6mm) can be used to accurately measure curved materials such as pipes.

(3) The detection surface is not parallel to the bottom surface, the sound wave encounters the bottom surface to generate scattering, and the probe cannot accept the bottom wave signal.

(4) Castings and austenitic steels are unevenly distributed or coarse grains. When electronic coating thickness gauge pass through them, they cause severe scattering attenuation. The scattered ultrasonic waves propagate along complicated paths, which may cause the echoes to annihilate, which is resulting in no display. A low-frequency coarse crystal dedicated probe (2.5MHz) is available.

(5) There is some wear on the probe contact surface. The surface of the commonly used thickness measuring probe is made of acryl resin. The long-term use will increase the surface roughness, resulting in a decrease in sensitivity, resulting in the incorrect display. It can be sanded with 500 sandpaper to make it smooth and ensure parallelism. If it is still unstable to consider replacing the probe.

(6)There are a large number of corrosion pits on the back of the object to be tested. Due to rust spots and corrosion pits on the other side of the object, the sound waves are attenuated, resulting in irregular readings, in extreme cases, no reading.

(7) There is sediment in the measurement object (such as pipeline). When the sediment and the acoustic impedance of the portable ultrasonic thickness gauges are not much different, the thickness gauge shows the wall thickness plus the thickness of the deposit.

(8) When there are defects inside the material (such as inclusions, interlayers, etc.), the displayed value is about 70% of the nominal thickness. At this time, the defect detection can be further performed by the ultrasonic flaw detector.