1. eddy current proximity switch This switch is sometimes called inductive proximity switch. It uses a conductive object to generate eddy current inside the object, and when it is close to the switch, it can generate electromagnetic field. Eddy current reacts on the proximity switch, changing the internal circuit parameters of the switch can identify whether there is a conductive object approaching, thus controlling the switch to be turned on or off. The object detected by the proximity switch must be conductive.
2. Capacitive proximity switch This kind of switch is usually measured by one board that constitutes the capacitor and another board that serves as the switch housing. During measurement, the housing is usually grounded or connected to the equipment housing. When an object approaches the switch, is it a conductor? Because of its proximity, the dielectric constant of the capacitor will change, so the capacitor will change, so the circuit state and probe will also change, so the switch can be turned on or off. The detection object of this proximity switch is not limited to conductors, and liquid or powder can be insulated.
3. The Hall element of the Hall proximity switch is a magnetic sensor. Switches made of Hall elements are called Hall switches. When an object is close to the Hall magnetic switch, the Hall element on the surface will detect the circuit state inside the switch, and the switch will change due to the Hall effect, so as to determine the existence near the magnetic object and then control the opening or closing. The detection object of the proximity switch must be a magnetic object.
4. photoelectric proximity switch A switch made of photoelectric effect is called photoelectric switch. The light-emitting device and the photoelectric device are installed in a certain direction of the same detection head. When the reflecting surface (the detected object) approaches, the photoelectric device receives the reflected light and outputs a signal, thus "sensing" the approaching object.
5. Thermoelectric proximity switch A switch consisting of elements that can sense temperature changes is called a thermoelectric proximity switch. In this switch, an exothermic electrical element is mounted on the detection surface of the switch. When objects with different ambient temperatures approach, the output of exothermic electrical components will change, so that the detected object can be closed.
6.TCK magnetic switch makes the sensor probe induce excitation current, the input frequency must be in the magnetic field without permanent magnet, and no output signal is found. When the test object (permanent magnet) moves to the detection area, the magnetic field of induced current is generated, and the excitation current is superimposed to generate a pulse signal. The induction coil inputs the processing pulse into the integrated circuit, drives the switching transistor, turns on, starts the relay action and outputs the signal. TCK- 1 p (normal, magnetic field signal detection starts, and reset is delayed for 2 seconds after deletion) TCK- 1 t (explosion-proof, signal is cut off for 2 seconds after signal detection) TCK-2 p (normal, direction detection, only magnetic field signal in specific direction of N-S, and reset is delayed for 2 seconds after signal removal). Only when the magnetic field signal in a specific direction of N-S is deleted, the signal will be reset after a delay of 2 seconds) TCK-3 p (normal, the magnetic field signal will be detected, and the magnetic reset will be detected again after deletion) TCK-3 t (explosion-proof, the magnetic field signal will be detected again after deletion), and then TCK-4 p (normal, only the magnetic field signal in a specific direction of N-S will be detected) will detect the magnetic field signal.
7. Other proximity switches When the distance between the observer or the system and the wave source changes, the frequency of the proximity wave will shift, which is the so-called Doppler effect. Sonar and radar are built by using this effect. Ultrasonic proximity switch and microwave proximity switch can be made by using Doppler effect. When an object approaches, the reflected signal received by the proximity switch will produce Doppler frequency shift, which can identify whether the object approaches.