The stability of the focal length of the laser cutting machine is very important in the cutting process, so the distance between the cutting head and the plate must be kept constant, which will directly affect the processing quality, so in order to improve the cutting quality and reduce the production 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 increase the safety of the process.
Displacement measurement is one of the most basic measurement work. according to whether the sensor is in contact with the measured workpiece, the displacement sensor can be divided into two types: contact sensor and non-contact sensor. The non-contact sensor has a fast dynamic response speed, low lag error, and even zero while ensuring high resolution.
The earliest application of a non-contact sensor, sometimes called a proximity sensor, is a proximity switch, that is, when the detected object is close to a certain distance from the sensor probe, the switch signal is given. at present, the proximity sensor has been developed to not only detect the existence of the object, but also give the distance between the object and the sensor probe, and provide information about the shape and spatial position of the workpiece.
Because it can be used to measure the displacement of moving objects, this kind of sensor is also called a non-contact displacement sensor. the commonly used displacement sensors are the hysteresis telescopic displacement sensor, eddy current displacement sensor, and capacitive displacement sensor. inductor displacement sensor and so on.
According to the principle of various sensors, the capacitive sensor has high sensitivity and has the following characteristics:
- Simple structure, strong adaptability, easy to manufacture, easy to ensure high precision, can be made into a small size sensor to achieve special measurement, can work in high and low temperature, strong radiation and strong magnetic field and another harsh environment, can withstand high pressure, high impact, overload and so on.
- The good dynamic response, because the electrostatic gravitation between the plates is very small, the activation energy required is very small, and its movable part can be done very small and thin, so its natural frequency is very high and the dynamic response time is short, and it can work at the frequency of several megahertz. It is especially suitable for dynamic measurement.
- The larger relative variation is only limited by the linear region, and its value can reach 100% or more, which can ensure the resolution and measuring range of the sensor.
- The heat is small and the temperature coefficient is small. Because the capacitance value of the capacitance sensor has nothing to do with the electrode material, the material with a low-temperature coefficient can be selected, which can ensure good stability when the external temperature is stable.