Principle of Ultrasonic Thickness Gauge and Coating Thickness Gauge
Ultrasonic thickness gauges are divided according to their working principles: there are 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 finish of the measured object, the ultrasonic pulse method for thickness measurement The instrument 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: transmitting circuit, receiving circuit, and counting display circuit. The high-voltage shock wave generated by the transmitting circuit excites the probe to generate ultrasonic transmitting pulse waves. The pulse waves are reflected by the medium interface and received by the receiving circuit. The liquid crystal display shows the thickness value, which is mainly based on the propagation speed of the sound wave in the sample multiplied by half of the time passing through the sample to obtain the thickness of the sample.
The HT series ultra-wave thickness gauge operated by our factory is a pocket-sized intelligent measuring instrument with low power consumption and low limit developed by single-chip technology on the basis of adopting advanced technology at home and abroad. It not only has instruments for measuring the thickness of different materials, And there are single-measure steel, ultra-thin, and can be equipped with high-temperature thickness-measuring probes.
2 Thickness Gauge Applications
Due to the convenience of ultrasonic treatment and good directivity, ultrasonic technology can measure the thickness of metal and non-metal materials, which is fast, accurate and pollution-free, especially in the occasions where only one side is allowed to be touched, it can show its superiority , widely used in various plate, pipe wall thickness, boiler container wall thickness and local corrosion, rust, so for metallurgy, shipbuilding, machinery, chemical industry, electric power, atomic energy and other industrial sectors of product inspection,
It plays a major role in the safe operation and modern management of equipment.
Ultrasonic cleaning and ultrasonic thickness gauge are only part of the application of ultrasonic technology, and there are many fields that can be applied to ultrasonic technology. Such as ultrasonic atomization, ultrasonic welding, ultrasonic drilling, ultrasonic grinding, ultrasonic liquid level gauge, ultrasonic level gauge, ultrasonic polishing, ultrasonic cleaning machine, ultrasonic motor and so on. Ultrasonic technology will be more and more widely used in all walks of life.
Working principle of eddy current coating thickness gauge
1. Basic principles
The basic working principle of the eddy current coating thickness gauge is that when the measuring head is in contact with the measured sample, the high-frequency electromagnetic field generated by the measuring head device causes the metal conductor placed under the measuring head to generate eddy current, and its amplitude and phase are the conductor It is a function of the thickness of the non-conductive coating between the eddy current and the probe. That is, the alternating electromagnetic field generated by the eddy current will change the parameters of the probe, and the size of the parameter variable of the probe, and convert this electrical signal to obtain the measured coating The thickness of the coating.
2. Reasons affecting measurement accuracy
(1) When the thickness of the covering layer is greater than 25 μm, the error is approximately proportional to the thickness of the covering layer;
(2) The electrical conductivity of the base metal has an influence on the measurement, which is related to the composition of the base metal material and the heat treatment method;
(3) Any kind of thickness gauge requires the base metal to have a critical thickness. Only when it is greater than this thickness, the measurement will not be affected by the thickness of the base metal;
(4) The eddy current thickness gauge has an edge effect on the sample determination, that is, the measurement near the edge of the sample or the inner corner is unreliable.
(5) The curvature of the sample has an influence on the measurement, and this influence will obviously increase with the decrease of the radius of curvature;
(6) The surface roughness of the base metal and the covering layer affects the accuracy of the measurement, and the increase in the roughness increases the impact;
(7) The eddy current thickness gauge is sensitive to the attached substances that prevent the close contact between the probe and the surface of the coating.
