# Why do the test results of a used car paint meter show negative numbers?

From:Linshang Time:2024/03/28 10:23:12 Browse:67

A car paint meter is an instrument used to detect the thickness of the car paint. Normally, it will display a positive value, that is, the thickness value. However, in the process of use, sometimes a negative number may appear, which may be caused by incorrect instrument calibration, uneven test position, zero adjustment, or instrument failure. How to solve this problem after a negative number appears? This article will tell you the answer.

## What is car paint meter?

The car paint meter refers to a special instrument that detects the paint thickness on the surface of a car. It can directly determine the sheet metal and paint condition of a car.

1.Working principle of car paint meter
The car paint meter is designed based on the Hall effect and eddy current principles, and can non-destructively detect the thickness of automobile paint. When measuring the ferrous body, the Hall effect principle is used. The instrument calculates the thickness of the coating on the car body surface by judging the strength of the magnetic induction. When the received magnetic field strength is weaker, it means that the probe is farther away from the car body base material, and the coating on the car body is thicker, and vice versa. When measuring aluminum car bodies, the eddy current principle is used. The probe of the instrument calculates the thickness of the car paint by judging the intensity of the received eddy current. The weaker the intensity of the eddy current received by the instrument probe, the farther the probe is from the vehicle body base material, which means the thinner the paint thickness.

2. Normal test result range of car paint meter
Generally, the normal test result range of Linshang car paint meter is between 0μm and 3500μm. The paint thickness of new cars is usually around 100μm to 150μm, and the paint thickness of vehicles that have been repaired or repainted may increase.If the test result is negative, it may be caused by the following reasons.

## What is the reason for the negative number on the car paint meter?

1. Instrument calibration problem: If the car paint meter is not calibrated correctly or there is a problem during the calibration process, the test results may be negative.
2. The test position is uneven: During the test, if the test position is uneven, or the car paint meter is not perpendicular to the surface of the test object, it may lead to inaccurate measurements and negative numbers.
3. Zero adjustment problem: If the zero adjustment operation is performed on a coated substrate, and then a thin car paint is measured, a negative number may appear. This is because the base number when zeroing is larger and the actual car paint is thinner, resulting in a negative measurement result.
4. Instrument failure: The car paint meter itself may malfunction, such as sensor damage, insufficient battery power, etc., which may also lead to negative test results.