What’s the detection methods for coating thickness measurement(2)

Eddy current thickness gauge:

Eddy current thickness gauges are generally used to measure the thickness of an insulating coating on a non-ferrous metal substrate. This method is also a non-destructive measurement method.The instrument uses a thin wire coil that conducts high frequency AC (above 1 MHz) to create an alternating magnetic field on the surface of the instrument probe. When the probe is near the conductive surface, the alternating magnetic field will form a vortex on the surface. The properties of the matrix material and the distance between the probe and the substrate (ie the thickness of the coating) affect the size of the eddy current. This eddy current in turn produces a relative electromagnetic field that can be sensed by the excitation coil or another adjacent coil. The appearance and operation of the eddy current gauge are similar to electromagnetic induction gauges. This type of instrument is capable of measuring the thickness of coatings on almost all non-ferrous metals. 

As with electro magnetic induction thickness gauges, they typically use a constant pressure probe and display the measurement on the LCD screen. In addition, they can choose to store measurements or analyze them instantly and output them to a printer or computer for further inspection. The measurement deviation is generally about ±1%. The test is sensitive to surface roughness,curvature, substrate thickness, type of metal substrate material, and its distance from the edge. The test method of ultrasonic paint thickness gauge can refer to ASTM B 244, ASTM D 7091 and ISO 2360 and other international standards. Many thickness gauges now combine the principles of electromagnetic induction and eddy currents into one system. Some simple measurement tasks can automatically switch from one operating principle to another to measure the coating thickness on most metals material. These integrated systems have been widely recognized and welcomed by the paint industry and the powder coating industry.

Third, ultrasonic thickness gauge

Ultrasonic echo pulse technology used in ultrasonic thickness gauges is generally used to measure the thickness of coatings on the surface of non-metallic matrix materials (such as plastics, wood, etc.) Moreover, this method is a non-destructive coating thickness gauge method and does not measure .The sample caused damage.The instrument's probe contains an ultrasonic transducer that emits pulses and passes through the coating. The pulse is reflected back from the substrate material to the transducer and converted to a high frequency electrical signal. By digitally analyzing the echo waveform, one can effectively determine the thickness of the coating. In some cases, the instrument can also measure the thickness of a single layer in a multilayer system. The measurement standard deviation of this method is generally about ± 3%, and the measurement method can refer to the ASTM D6132 international standard.
 
Four, micrometer thickness gauge