Type of proximity switch
1. Eddy current proximity switch
This switch is sometimes called inductive proximity switch. It uses the conductive object to generate eddy current inside the object when approaching the proximity switch that can generate electromagnetic field. This eddy current reacts on the proximity switch to change the internal circuit parameters of the switch, thereby identifying whether conductive objects are moving close, and then controlling the on-off of the switch. The object that can be detected by the proximity switch must be a conductor.
2. Capacitive proximity switch
The measurement of the switch is usually one electrode plate of the capacitor, and the other electrode plate is the shell of the switch. During measurement, the enclosure is usually grounded or connected to the enclosure of the equipment. When an object moves to the proximity switch, whether it is a conductor or not, because of its proximity, it will always change the dielectric constant of the capacitance, thus changing the electrical capacity, changing the circuit state connected to the measuring head, so as to control the opening or closing of the switch. The objects detected by proximity switches are not limited to conductors, insulating liquids or powders.
3. Hall proximity switch
Hall element is a magnetic sensor. The switches made of Hall elements are called Hall switches. When the magnetic object is close to the Hall switch, the Hall element on the detection surface of the switch changes the internal circuit state of the switch due to the Hall effect, so as to identify the surrounding magnetic objects, and then control the switch or disconnect. The detection object of the proximity switch must be a magnetic object.
4. Photoelectric proximity switch
The switch made of photoelectric effect is called photoelectric switch. Light emitting devices and photoelectric devices are installed in the unified detection head. When the reflecting surface (the object to be detected) approaches, the photoelectric device will output a signal after receiving the reflected light, so that the object can be "sensed".
5. Pyroelectric proximity switch
The switch made of components that can sense temperature changes is called pyroelectric proximity switch. The pyroelectric device is installed on the detection surface of the switch. When approaching an object with different ambient temperatures, the output of the pyroelectric device will change, thus detecting the object approaching.
6. Other types of proximity switches
When the observer or system changes the wave source spacing, the frequency of the approaching wave is called Doppler effect. Sonar and radar are made by using the principle of this effect. Ultrasonic proximity switch and microwave proximity switch are all made by using Doppler effect. When the object moves nearby, the reflected signal received by the proximity switch will generate Doppler frequency shift, so as to determine whether the object is close
