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The classification of the proximity switch(1)

Passive proximity switch
This switch does not need power supply, and the closed state of the switch is controlled by magnetic induction. When the magnetic or iron trigger is close to the switch magnetic field, it acts with the internal magnetic force of the switch to control the closing. Features: no power supply, non-contact, maintenance free, environmental protection.

Eddy current proximity switch
This kind of switch is sometimes called inductive proximity switch. It uses a conductive object to generate eddy current inside the object when it approaches the proximity switch that can generate electromagnetic field. The eddy current reacts on the proximity switch to change the internal circuit parameters of the switch, so as to identify whether there is a conductive object approaching, and then control the on or off of the switch. The object that can be detected by this proximity switch must be a conductor.

1. Principle: the oscillator is composed of inductance coil, capacitor and transistor, and generates an alternating magnetic field. When a metal object approaches this magnetic field, eddy current will be generated in the metal object, resulting in the stop of oscillation. This change is amplified by the rear pole and converted into transistor switching signal output.

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

3. It is applied to various mechanical equipment for position detection, counting signal pickup, etc.

Capacitive proximity switch
The measurement of this switch is usually one plate constituting the capacitor, and the other plate is the shell of the switch. The enclosure is usually grounded or connected to the enclosure of the equipment during measurement. When an object moves to the proximity switch, whether it is a conductor or not, due to its proximity, it is always necessary to change the dielectric constant of the capacitance, so as to change the capacitance and the state of the circuit connected to the measuring head, so that the connection or disconnection of the switch can be controlled. The detection object of this proximity switch is not limited to conductors, insulating liquids or powders, etc.