Working principle and design scheme of ultrasonic thickness gauge

According to the working principle, ultrasonic thickness gauges are divided into several methods: 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 object being measured, the ultrasonic pulse method thickness gauge is the most popular instrument among users.

　　1. Working principle

　　The ultrasonic thickness gauge mainly consists 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 transmission pulse wave. The pulse wave is reflected by the medium interface and received by the receiving circuit. After being counted and 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 wave thickness gauge is a low-power, low-limit, pocket-sized intelligent measuring instrument developed using single-chip microcomputer technology based on the use of 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 types, 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 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 where ultrasonic technology can be applied. 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.

　　3. Factors affecting measurement accuracy

　　(1) When the coating thickness is greater than 25 μm, the error is approximately proportional to the coating thickness;
　　(2) The conductivity of the base metal affects the measurement, which is related to the base metal material composition and heat treatment method;
　　(3) Any thickness gauge requires that the base metal has a critical thickness. Only when the thickness is greater than this critical thickness will the measurement 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 sample edge or inner corner is unreliable;
　　(5) The curvature of the sample affects the measurement, and this effect will increase significantly with the decrease of the curvature radius;
　　(6) The surface roughness of the base metal and the coating affects the measurement accuracy. The effect increases with the increase of the roughness.