Electrical Encyclopedia: What are the types of magnetic proximity switches?
Because the displacement sensor can be made according to different principles and different methods, and different displacement sensors have different "perception" methods for objects, so the common proximity switches are as follows:
Eddy current proximity switch
This type of switch is sometimes called an inductive proximity switch. It uses a conductive object to generate an electromagnetic field near this.
When the switch is approached, eddy currents are generated inside the object. This eddy current reacts to the proximity switch, causing the internal circuit parameters of the switch to change, thereby identifying the presence or absence of the conductive object moving closer, thereby controlling the on or off of the switch. The object that this proximity switch can detect must be an electrical conductor.
Capacitive proximity switch
The measurement of such a switch is usually one plate constituting the capacitor, and the other plate is the outer casing of the switch. This housing is usually grounded or connected to the housing of the device during the measurement process. When an object moves toward the proximity switch, whether it is a conductor or not, due to its proximity, the dielectric constant of the capacitor is always changed, so that the capacitance changes, so that the state of the circuit connected to the measuring head also occurs. Change, thereby controlling the switch to be turned on or off. The object to be detected by the proximity switch is not limited to a conductor, a liquid or powder that can be insulated, or the like.
Hall proximity switch
The Hall element is a magnetic sensing element. A switch made of a Hall element is called a Hall switch. When the magnetic object moves closer to the Hall switch, the Hall element on the switch detection surface changes the internal circuit state of the switch due to the Hall effect, thereby identifying the presence of a magnetic object nearby, thereby controlling the on or off of the switch. The detection object of such a proximity switch must be a magnetic object.
Photoelectric proximity switch
A switch made using the photoelectric effect is called a photoelectric switch. The illuminating device and the optoelectronic device are mounted in the same detecting head in a certain direction. When a reflective surface (object to be detected) approaches, the optoelectronic device receives the reflected light and outputs it at the signal, thereby "perceiving" that an object is approaching.
Pyroelectric proximity switch
A switch made of a component that senses temperature changes is called a pyroelectric proximity switch. This type of switch is to mount the pyroelectric device on the detecting surface of the switch. When there is an object close to the ambient temperature, the output of the pyroelectric device changes, thereby detecting the proximity of an object.
TCK magnetic switch
The magnetic fluxgate technology is used to manufacture the induction probe, and the excitation current of a certain frequency is input. When the magnetic field of the permanent magnet is not detected, there is no output signal. When the detected object (permanent magnet) moves to the detection area, the magnetic field generates an induced current, and The excitation current is superimposed to generate a signal pulse. The induction coil inputs the pulse into the IC for processing, drives a switching transistor to turn it on, activates a relay action, and outputs a signal.
TCK-1P (common type, detects the start of the magnetic field signal, delays 2 seconds after the signal is removed)
TCK-1T (explosion-proof type, detects the start of the magnetic field signal, delays 2 seconds after the signal is removed)
TCK-2P (common type, with direction detection, only starts the magnetic field signal of NS specific motion direction, delays 2 seconds after the signal is removed)
TCK-2T (explosion-proof type, with direction detection, only the magnetic field signal of NS specific motion direction is activated, and the signal will be delayed by 2 seconds after the signal is removed)
TCK-3P (common type, detects the start of the magnetic field signal, keeps the signal after the signal is removed, resets after detecting the magnetic field again) TCK-3T (explosion-proof type, detects the start of the magnetic field signal, keeps the signal after the signal is removed, and detects the magnetic field again Reset)
TCK-4P (common type, with direction detection, only activates the magnetic field signal of NS specific motion direction, keeps the signal after it is removed, and resets when the magnetic field signal is detected again)
TCK-4T (explosion-proof type, with direction detection, only the magnetic field signal of NS specific motion direction is activated, the signal is retained after being removed, and will be reset when the magnetic field signal is detected again)
Other proximity switches
When the distance of the observer or system to the wave source changes, the frequency of the approaching wave shifts. This phenomenon is called the Doppler effect. Sonar and radar are made using the principle of this effect. Ultrasonic proximity switches, microwave proximity switches, etc. can be made using the Doppler effect. When an object moves closer, the reflected signal received by the proximity switch generates a Doppler shift, thereby identifying the presence or absence of an object approaching.
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