Working Principle of Ultrasonic Thickness Gauge/Coating Thickness Gauge

Ultrasonic thickness gauges are divided into several types according to their working principles: resonance method, interference method and pulse reflection method. Since the pulse reflection method does not involve the resonance mechanism and is not closely related to the surface smoothness of the object being measured, the ultrasonic pulse thickness gauge is the most popular instrument among users.

1 Working Principle
The ultrasonic thickness gauge is mainly composed of two parts: the host and the probe. The host circuit includes three parts: the transmitting circuit, the receiving circuit, and the counting and display circuit. The high-voltage shock wave generated by the transmitting circuit excites the probe to generate an ultrasonic pulse wave. The pulse wave is reflected by the medium interface and received by the receiving circuit. After being processed by the single-chip microcomputer, the thickness value is displayed on the LCD display. It mainly obtains the thickness of the sample based on the propagation speed of the sound wave in the sample multiplied by half of the time it passes through the sample.
The HT series ultrasonic thickness gauge operated by our factory is a low-power, low-low limit pocket-sized intelligent measuring instrument developed using single-chip microcomputer technology on the basis of adopting advanced domestic and foreign technologies. It not only has instruments for measuring the thickness of different materials, but also has single-measurement steel and ultra-thin ones, and can be equipped with high-temperature thickness measuring probes.
2 Application fields of thickness gauges
Since ultrasonic processing is convenient and has good directivity, ultrasonic technology can measure the thickness of metal and non-metal materials quickly, accurately and without pollution, especially in situations where only one side can be touched. It can better show its superiority. It is widely used in various plates, pipe wall thickness, boiler container wall thickness and local corrosion and rust. Therefore, it
plays a major role in product inspection in various industrial sectors such as metallurgy, shipbuilding, machinery, chemical industry, electric power, atomic energy, etc., and in the safe operation and modern management of equipment.
Ultrasonic cleaning and ultrasonic thickness gauges are only part of the application of ultrasonic technology. There are many other fields that can apply ultrasonic technology. For example, ultrasonic atomization, ultrasonic welding, ultrasonic drilling, ultrasonic grinding, ultrasonic level meter, ultrasonic level meter, ultrasonic polishing, ultrasonic cleaning machine, ultrasonic motor, etc. Ultrasonic technology will be more and more widely used in all walks of life.

Working principle of eddy current coating thickness gauge
1. Basic principle The
basic working principle of eddy current coating thickness gauge is that when the probe contacts the sample to be measured, the high-frequency electromagnetic field generated by the probe device causes the metal conductor placed under the probe to generate eddy currents, whose amplitude and phase are functions of the thickness of the non-conductive coating between the conductor and the probe. That is, the alternating electromagnetic field generated by the eddy current will change the probe parameters, and the size of the probe parameter variable, and the thickness of the measured coating can be obtained by converting and processing this electrical signal.
2. Reasons affecting measurement accuracy
(1) When the coating thickness is greater than 25μm, its error is approximately proportional to the coating thickness;
(2) The conductivity of the base metal has an effect on the measurement, which is related to the composition of the base metal material and the heat treatment method;
(3) Any thickness gauge requires that the base metal has a critical thickness. Only when the thickness is greater than this, the measurement will not be affected by the base metal thickness;
(4) The eddy current thickness gauge has an edge effect on the sample measurement, that is, the measurement near the edge of the sample or the inner corner is unreliable.
(5) The curvature of the sample has an impact on the measurement, and this impact will increase significantly as the radius of curvature decreases;
(6) The surface roughness of the base metal and the coating affects the measurement accuracy. The greater the roughness, the greater the impact;
(7) The eddy current thickness gauge is sensitive to attached materials that prevent the probe from closely contacting the coating surface. Therefore,
the dirt on the probe and the coating surface should be removed before measurement; during measurement, the probe should maintain constant pressure and vertical contact with the test surface.