Difference between Magnetic and Eddy Current Paint Film Thickness Gauge

Magnetic paint film thickness gauges and eddy current dry film gauges are one of the coating thickness gauges that can be used to measure the metal substrate coating thickness. But the two instruments use different measurement principles for different situations. Below, we will introduce the difference between the principle and the application.

1.Measurement principle

(1)Measuring principle of magnetic paint film thickness gauge

The magnetic paint film thickness gauge uses the magnetic method to measure the thickness of the coating.The magnetic principle is divided into two types. Therefore, the magnetic paint film thickness gauge is also divided into a magnetic coating thickness gauge and a magnetic induction coating thickness gauge.

The magnetic corrosion thickness gauge can judge the thickness of the coating by the magnetic force between the permanent magnet and the magnetic metal substrate in the probe. The paint film thickness gauge is mainly composed of a force spring, a magnetic steel, a scale and a self-stop mechanism. After the partial magnetic composition, the measured magnetic metal substrate and the magnetic steel are attracted. The relay spring is gradually elongated. When the tensile force is gradually increased to be just greater than the suction force, the magnetic steel will be separated from the magnetic metal substrate. And the momentary pulling force is released. The size can be recorded and the coating thickness can be measured by a certain proportional relationship.

The magnetic induction paint film thickness gauge utilizes the principle of magnetic induction to determine the coating thickness by measuring the magnetic flux of the permanent magnet in the probe through the non-ferromagnetic coating into the magnetic metal substrate. Similarly,the thicker the coating, the smaller the magnetic flux.Finally,we get a certain proportional relationship to calculate the coating thickness.

Since the magnetic induction has less test conditions than the magnetic paint film thickness gauge,the application of the magnetic induction method is more extensive.

(2)Measurement principle of eddy current paint thickness gauge

The eddy current paint film thickness gauge adopts the principle of eddy current. When the coil core in the probe is energized, a high-frequency magnetic field can be generated. The eddy current generated by the contact between the probe and the metal substrate of the tested coating reflects the probe and the substrate. The closer the distance between the probes and the metal substrate, the larger the eddy current, the smaller the eddy current. Based on this principle, the proportional relationship between the eddy current size and the distance can be found. Then the distance can be determined. That is the thickness of the coating.

2. Application area of paint film thickness gauge

(1)Application field of magnetic paint film thickness gauge

According to the principle of magnetic attraction and magnetic induction method, the magnetic paint film thickness gauge is suitable for measuring the thickness of non-magnetic coating on magnetic metal substrate, mainly used for glazed porcelain, enamel protective layer, nickel chrome, etc. Non-ferrous metal coatings, paints and thickness measurements of some anti-corrosion coatings. There are also some plastic, capacitor paper, polyester film and other materials, you can also use the steel substrate to achieve its thickness measurement.

(2)Application field of eddy current paint film thickness gauge

An eddy current paint film thickness gauge is suitable for measuring the thickness of a non-conductive coating on a non-magnetic metal substrate. The main application is the measurement of the coating thickness, ceramics or anodized layers on non-magnetic metal substrates (such as copper, aluminum, die-cast zinc).