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How many kinds of the proximity switch

- May 11, 2018 -

Passive proximity switch

This switch does not require a power supply and controls the closed state of the switch through magnetic induction. When the magnetic or iron trigger is close to the switching magnetic field, the internal magnetic force of the switch controls the closing. Features: No power, no contact, no maintenance, environmental protection.


Eddy current proximity switch

This type of switch is sometimes called an inductive proximity switch. It is the use of conductive objects in the proximity of this can generate electromagnetic field proximity switches, so that the object generates eddy currents. This eddy current reacts to the proximity switch, causing the internal circuit parameters of the switch to change, thereby recognizing whether or not the conductive object is moving closer, thereby controlling the on and off of the switch. The object that this proximity switch can detect must be a conductor.

1. Principle: An oscillator is composed of an inductor coil, a capacitor and a transistor, and an alternating magnetic field is generated. When a metal object approaches this magnetic field, eddy currents are generated in the metal object, causing the oscillation to stop. This change is caused by After the amplifying process, it is converted into a transistor switching signal output.

2. Features: A, good anti-interference performance, high switching frequency, greater than 200HZ. B, can only sense the metal

3. Applicable to various machinery and equipment for position detection, counting signal picking and so on.



Capacitive proximity switch

The measurement of such a switch is usually one plate constituting a capacitor, and the other plate is the housing of the switch. This enclosure is usually grounded or connected to the enclosure 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 always changes, so that the capacitance changes, and the state of the circuit connected to the measuring head also occurs. Changes, which can control the switch on or off. The object to be detected by this proximity switch is not limited to a conductor, an insulating liquid, a powder, or the like.


Hall proximity switch

The Hall element is a magnetosensitive element. A switch made using a Hall element is called a Hall switch. When the magnetic object moves close to the Hall switch, the Hall element of the switch detection surface changes the internal circuit state of the switch due to the generation of the Hall effect, thereby recognizing the presence of a magnetic object nearby, thereby controlling the on and off of the switch. The proximity switch must be a magnetic object.


Photoelectric proximity switch

Switch made of photoelectric effect is called photoelectric switch. The light emitting device and the optoelectronic device are mounted in the same test head in a certain direction. When there is a reflective surface (detected object) approaching, the optoelectronic device receives the reflected light and then outputs the signal, thereby "sensing" the approach of the object.


Other types

When the observer or system changes the distance of the wave source, the frequency of the approaching wave will shift. 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 there is an object approaching, the Doppler frequency shift is generated by the reflected signal received by the proximity switch, so that the presence or absence of the object can be identified.




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