Coating thickness gauge classification and measurement principle Coatings that protect and decorate the surface of materials, such as coatings, coatings, coatings, laminates, chemical film, etc., are referred to as coatings in relevant national and international standards. Coating thickness measurement has become an important part of the processing industry and surface engineering quality inspection, and is an essential means for products to achieve superior quality standards. In order to make the products internationalized, China's export commodities and foreign-related projects have clear requirements for the thickness of the coating. X-ray and beta ray methods are non-contact and non-destructive measurements, but the device is complex and expensive, and the measurement range is small. Due to radioactive sources, users must observe radiation protection regulations. The X-ray method can measure extremely thin coatings, double coatings, and alloy coatings. The beta ray method is suitable for the measurement of coatings with atomic number greater than 3 in coatings and substrates. The capacitance method is used only when the thickness of the insulating coating of the thin conductor is measured. one. Magnetic force measurement principle and thickness gauge two. Magnetic induction measurement principle three. Eddy Current Measurement Principle The eddy current thickness gauge can measure the non-conductor coating on all electrical conductors, such as the surface of spacecraft, vehicles, household appliances, aluminum alloy doors and windows, and other aluminum products. Anodized film. The coating material has a certain conductivity, and can also be measured by calibration. However, the conductivity ratio of the two materials is required to be at least 3-5 times different (such as chrome plating on copper). Although steel substrates are also electrical conductors, this type of task is more appropriately measured using magnetic principles . Hydraulics Parts For Caterpillar Hydraulics Parts For Caterpillar ,Caterpillar Hydraulic Parts,Caterpillar Hydraulic Pump Spare Parts,Caterpillar Hydraulic Pump Parts Hangzhou Holdwell Mechanical&Electrical Co.,LTD , https://www.dieselpart.nl
Coating thickness measurement methods include: wedge cutting method, optical cutting method, electrolytic method, thickness difference measuring method, weighing method, X-ray fluorescence method, β-ray backscattering method, capacitance method, magnetic measurement method and eddy current measurement Law and so on. The first five of these methods are lossy detections, and the measurement methods are cumbersome and slow. They are mostly suitable for sampling inspections.
With the advancement of technology, especially after the introduction of microcomputer technology in recent years, thickness gauges using magnetic methods and eddy current methods have taken a step toward miniaturization, intelligence, multi-function, high-precision, and practical application. The resolution of the measurement has reached 0 . 1 micron, accuracy can reach 1%, with a substantial increase. Its wide application scope, wide range, easy operation and low cost make it the most widely used thickness measurement instrument in industry and scientific research .
The use of non-destructive methods neither destroys the cladding nor destroys the substrate, and the detection speed is fast, enabling a large amount of detection work to be carried out economically.
Measuring principle and instrument
The magnitude of the suction between the permanent magnet (probe) and the magnetically conductive steel is proportional to the distance between the two. This distance is the thickness of the coating. Using this principle, thickness gauges can be manufactured , as long as the difference between the magnetic permeability of the coating and the substrate is sufficiently large. Since most industrial products use structural steel and hot-rolled cold-rolled steel sheets for stamping, magnetic thickness gauges are the most widely used. The basic structure of the thickness gauge consists of magnetic steel, relay spring, ruler and self-stop mechanism. After the magnetic steel and the object to be measured are attracted, the measuring spring is gradually elongated thereafter, and the pulling force gradually increases. When the pulling force is just greater than the suction force, the thickness of the coating can be obtained by recording the magnitude of the pull-down force at the moment when the magnet is detached. New products can automate this recording process. Different models have different ranges and applications.
This instrument is characterized by simple operation, robustness, no power supply, no calibration before measurement, and low price, which is very suitable for on-site quality control in the workshop.
In the magnetic induction principle, the thickness of the coating is measured by the magnitude of magnetic flux flowing from the probe through the non-ferromagnetic coating into the ferromagnetic base. The size of the magnetic resistance corresponding to it can also be measured to indicate the thickness of its coating. The thicker the coating, the greater the magnetic resistance and the smaller the magnetic flux. The thickness gauge using the principle of magnetic induction can, in principle, have a non-magnetically conductive coating thickness on a magnetically conductive substrate. General requirements for substrate magnetic permeability above 500. If the cladding material is also magnetic, the difference in magnetic permeability from the substrate is required to be sufficiently large (eg, nickel plating on steel). When the probe on the soft core is placed on the measured sample, the instrument automatically outputs the test current or test signal. Early products use an analog meter to measure the magnitude of the induced electromotive force. The instrument amplifies the signal and then instructs the thickness of the coating. In recent years, circuit designs have introduced new technologies such as frequency stabilization, phase lock, and temperature compensation, and use magnetic resistance to modulate measurement signals. It also uses a patented integrated circuit designed to introduce microcomputers, which has greatly improved measurement accuracy and reproducibility (almost one order of magnitude). Modern Magnetic Induction Thickness Gauge with Resolution up to Magnetic Induction Thickness Gauge_Electrical Eddy Current Measuring Principle_Magnetic Force Measuring Principle and Thickness Gauge_Electrical Eddy Current Principle Thickness Gauge to 0 . 1um, the allowable error is 1%, and the range is 10mm.
The magnetic principle thickness gauge can be used to accurately measure the paint layer on the steel surface, porcelain, enamel protective layer, plastic, rubber coating, all kinds of non-ferrous metal plating layer including nickel and chromium, and various anti-corrosion coatings for chemical oil industry. Floor.
The high-frequency AC signal generates an electromagnetic field in the probe coil. When the probe is close to the conductor, eddy currents form in it. The closer the probe is to the conductive substrate, the larger the eddy current and the larger the reflection resistance. This amount of feedback quantifies the distance between the probe and the conductive substrate, that is, the thickness of the non-conductive coating on the conductive substrate. Because this type of probe measures the thickness of the coating on a non-ferromagnetic metal substrate, it is often referred to as a non-magnetic probe. Non-magnetic probes use high-frequency materials for coil cores, such as platinum-nickel alloys or other new materials. Compared with the principle of magnetic induction, the main difference is that the probe is different, the frequency of the signal is different, and the size and scale of the signal are different. Like the magnetic induction thickness gauge , the eddy current thickness gauge also achieves a resolution of 0 . 1um, allowable error 1%, high level of 10mm.