Can We Use Auto Paint Meter Test Plastic Bumper?

a. Magnetic auto paint meter principle

Magnetic auto paint meter is suitable for measuring the non-magnetic coating thickness on magnetic metal substrates. It is based on measuring the coating film thickness by using the magnetic flux of the probe through the non-ferromagnetic coating to enter the ferromagnetic substrate. The coating thickness can also be determined by measuring the magnitude of the magnetic resistance corresponding to the threshold. A static magnet is mounted on a balanced arm and therefore the force required to tug this magnet from the coating surface may be a measure of the coating thickness. Force is applied through a helical spring attached to the balanced arm at one end and to a scale wheel at the opposite . Due to that the scale wheel is turned the force is progressively increased until the magnet lifts from the coating surface. the size is drawn in thickness units instead of force and therefore the coating thickness are often read against a pointer on the case of the instrument.

b. Eddy current auto paint meter principle

Eddy current auto paint meter is used to measure non-conductive coating thickness on non-magnetic metal substrates. The coil core in the eddy current coating thickness gauge probe is usually made of a high-frequency material such as platinum-nickel alloy, which generates a high-frequency electromagnetic field in the coil by the current. After contacting of the conductor (metal substrate) at the probe and the bottom, eddy currents are formed on the metal substrate. The substrate characteristics and therefore the distance of the probe from the substrate (the coating thickness) affect the magnitude of the eddy currents. The eddy currents create their own opposing electromagnetic field which will be sensed by the exciting coil or by a second, adjacent coil. Eddy current auto paint meters look and operate like electronic magnetic gages. Like magnetic electronic gages, they commonly use a continuing pressure probe and display results on an LCD. They will even have options to store measurement results or perform instant analysis of readings and output to a printer or computer for further examination. the standard tolerance is ±1%. Testing is sensitive to surface roughness, curvature, substrate thickness, sort of metal substrate and distance from a foothold.

(2) Ultrasonic auto paint meter principle

Plastics, which are not electrically conductive in our lives, are insulators and do not generate magnetic fields. Therefore, this situation does not apply to the principle of Fe Hall effect and NFe eddy current. Therefore, plastic bumpers cannot be measured with the magnetic and eddy current auto paint meter.

If you want to measure the coating thickness on plastics, ultrasonic auto paint meter is recommended.   An ultrasonic technique is used when measuring the paint thickness over non-metal substrates such as plastic and fiberglass. The probe of the auto paint meter contains an ultrasonic transducer that sends a pulse through the coating. The pulse reflects back from the substrate to the transducer and is converted into a high frequency electrical signal that is analyzed to determine coating thickness. In some circumstances, individual layers in a multi-layer system can be measured. Prices range between $1,800 and $4,000.