In the cutting process of laser cutting machine, the distance between the cutting head and the workpiece and the perpendicularity between the nozzle and the workpiece surface are two important factors. It directly affects the processing quality, so in order to improve the cutting quality and reduce the generation of waste products, it is necessary to install some special sensors on the cutting head to ensure that it can produce stable and consistent cutting quality and can increase the process safety.

When the shape of the laser cutting head changes and the surface is uneven, the sensor automatically detects the change and automatically adjusts the height according to the change, so that it always keeps the same distance from the surface of the workpiece. It can process materials faster without continuous supervision. The displacement sensor used at home and abroad today is basically capacitive, its structure and shape are compatible with the processing head, and it is equipped with a detection signal processing unit.

Displacement measurement is a basic measurement work. According to whether the sensor is in contact with the measured workpiece, the displacement sensor can be divided into contact type and non-contact type. Compared with the contact type sensor, the non-contact type sensor has fast dynamic response speed, low hysteresis error, or even zero while ensuring high resolution.

Non-contact sensor, sometimes called proximity sensor, is used in the switching field, that is, when the detected object is close to a certain distance from the sensitive probe, the switch signal is given. The current proximity sensor has developed to not only detect the presence of an object, but also give the distance between the object and the sensitive probe, and can provide information about the shape and spatial position of the workpiece.

Because it can be used to measure the displacement of moving objects, this type of sensor is also called non-contact displacement sensor. The commonly used displacement sensors include magnetostrictive displacement sensor, eddy current displacement sensor, capacitive displacement sensor, inductor displacement sensor, etc.

According to the principle of various sensors, the capacitance sensor has high sensitivity and the following characteristics:

1. The dynamic response is good. Because the electrostatic attraction between the plates is very small, the action energy required is very small, and the movable part can be made very small and thin, so its natural frequency is very high, the dynamic response time is short, and it can work at a frequency of several megahertz, especially suitable for dynamic measurement.

2. Simple structure, strong adaptability, easy manufacturing, easy to ensure high accuracy, can be made into small size sensors to achieve special measurement, can work in high and low temperature, strong radiation, strong magnetic field and other harsh environments, can withstand high pressure, high impact, overload, etc.

3. Low heat generation and low temperature coefficient. Since the capacitance value of the capacitance sensor is independent of the electrode material, the material with low temperature coefficient can be selected, which can ensure good stability under the stable external temperature.

4. The larger relative variation is only limited by the linear region, which can ensure the resolution and measurement range of the sensor.