Measuring Methods of the Thickness Measuring Gauge and Its Advantages and Disadvantages

1. Measuring methods of the coating thickness instrument

1) Magnetic thickness measuring method: the suction force between the permanent magnet (probe) and the magnetically conductive steel is proportional to the distance between the two, which is the thickness of the coating.

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The magnetic coating thickness gauge is composed of magnetic steel, a relay spring, a ruler, and an automatic stop mechanism. After the magnet and the object to be measured are attracted, the measuring spring is gradually elongated, and the pulling force is gradually increased. When the pulling force is just greater than the suction force, the thickness of the coating can be obtained by recording the pulling force at the moment when the magnetic steel is detached.

2) Eddy current thickness measuring method: the high-frequency AC signal generates an electromagnetic field in the coil of the thickness-measuring gauge probe. When the probe is close to the conductor, an eddy current is formed in it.

The closer the probe is to the conductive substrate, the greater the eddy current and the reflection impedance are. Based on this principle, the feedback action of the thickness measuring gauge characterizes the distance between the probe and the conductive substrate, that is, the thickness of the non-conductive coating on the conductive substrate.

Because these probes are designed to measure the thickness of coatings on non-ferromagnetic metal substrates, they are often referred to as non-magnetic probes. Non-magnetic probes use high-frequency materials as coil cores, such as platinum-nickel alloys or other new materials.

2. The advantages and disadvantages of measuring methods of the coating thickness instrument

The magnetic thickness measuring method is suitable for the thickness measurement of non-magnetic conductive layers on magnetic conductive materials. Magnetic materials are generally: steel, iron, silver, and nickel. This method has high measurement accuracy.

The main difference between the eddy current thickness measuring method and the magnetic induction principle is different probes, different frequencies of the signal, and different magnitude and scale relationships of the signal. Like the digital thickness gauge meter using magnetic induction, the eddy current thickness measuring gauge also achieves a high resolution of 0.1um, an allowable error of 1%, and a range of 10mm. (You may also be interested in digital hardness testers)

The thickness measuring gauge using the eddy current principle can measure the non-conductive coating on all conductors in principle, such as paint, plastic coating, and anodic oxide film on the surface of aerospace aircraft, vehicles, household appliances, aluminium alloy doors and windows, and other aluminium products.

The cladding material has a certain conductivity, which can also be measured by calibration, but the ratio of the conductivity of the two is required to be at least 3-5 times different (such as chrome plating on copper). Although the steel substrate is also an electrical conductor, it is more suitable for such tasks to be measured by a magnetic thickness measuring gauge.

The eddy current thickness measurement is suitable for measuring the thickness of non-conductive layers on conductive metals, but this method is less accurate than the magnetic thickness measuring method.

With the increasing advancement of technology, especially after the introduction of microcomputer technology in recent years, the thickness measuring gauge using the magnetic method and eddy current method has taken a step forward in the direction of miniaturization, intelligence, multi-function, high precision, and practicality.

The resolution of the measurement has reached 0.1 microns, and the accuracy can reach 1%, which has been greatly improved. It has a wide range of applications, a wide measuring range, easy operation, and a low price, and is the most widely used thickness-measuring gauge in industry and scientific research.

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Magnetic induction coating thickness gauge is a common coating thickness gauge instrument, and it is also a more commonly used measurement method in the industry, that is, using the principle of magnetic induction, the size of the magnetic flux flowing from the magnetic head through the non-ferrous coating into the ferromagnetic substrate , Determine the thickness of the coating. Therefore, the magnetic thickness gauge can be used to measure the paint layer, plastic, rubber coating on the surface of steel, and the non-ferrous metal plating layer of nickel-chromium metal. It is widely used in the measurement of the coating thickness of steel components in engineering.

Magnetic induction coating thickness gauge can help companies control production standards and control production costs. General quality inspectors can also be used to detect whether objects meet delivery standards. In the used car industry, it can allow appraisers to inspect cars more scientifically and more effectively. fast.

So are there any disadvantages of magnetic induction coating thickness gauge?

1. Magnetic induction coating thickness gauge is a kind of dry film thickness gauge, so it can only be measured after the coating is cured, so it is more used in the post-production and quality inspection links.

2. The roughness of the substrate surface will affect the accuracy of the measurement results.

3. Even the magnetic induction coating thickness gauge with split probe design is still limited by the geometric shape of the parts, such as the measurement of the curved surface, the thickness of the substrate, or the inaccurate edge position.

4. The magnetic induction coating thickness gauge is limited by the material of the substrate and cannot accurately measure the magnetic metal substance on the coating.

Advantages of Magnetic Induction Coating Thickness Gauge:

1. The instrument has ultra-high precision and can measure thickness as low as 0.1μm;

2. The magnetic coating thickness gauge is mainly compact, flexible and easy to carry, and the price is relatively cheap;

3. The coating can be measured non-destructively and quickly.

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