Damaged or not? It is the main question buying a second-hand car. Identify hidden damage of the body is possible in various ways, but lately consumers are increasingly beginning to use thickness gauges. These are special devices that allow you to measure the thickness of paint. However, not all of them are equally effective.
Magnetic thickness gauge. The body of the device has hidden magnet, which is mechanically connected with an arrow-pointer. As closer the magnet is to the metal, so greater is its attraction and greater the angle of deflected arrow.
Electromagnetic thickness gauge. These devices operate on the basis of the Hall sensors or on the principle of electromagnetic induction.
Eddy current thickness gauges. The eddy currents create their own opposing electromagnetic fields that can be measured by the primary or secondary winding. Such devices are used for highly conductive surfaces, in particular, made of non-ferrous metals (such as aluminum, which is used in high-end car brands: Mercedes, BMW, Volvo, etc.).
There are also ultrasonic thickness gauges that measure the time until the arrival of the reflected ultrasound pulse.