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The working principle of Proximity Switch

- Apr 13, 2018 -

Proximity switch

Hall switch operation principle

First, the principle of introduction When a current through the metal or semiconductor sheet vertically placed in the magnetic field, the potential difference between the two ends of the sheet, this phenomenon is called the Hall effect. The potential difference between the two ends is called the Hall potential U, and the expression is that K is the Hall coefficient, I is the current passing through the slice, B is the magnetic induction intensity of the applied magnetic field (Lorrentz), d is The thickness of the sheet. It can be seen that the sensitivity of the Hall effect is directly proportional to the magnetic induction intensity of the applied magnetic field. The Hall switch belongs to such an active magnetoelectric conversion device. It is based on the Hall effect principle and is manufactured using an integrated package and assembly process. It can easily convert magnetic input signals into electricity in practical applications. Signals, at the same time, have the requirements of practical applications for easy operation and reliability in industrial applications. The input of the Hall switch is characterized by magnetic induction B. When the B value reaches a certain level (such as B1), the internal switch of the Hall switch is turned over, and the state of the output level of the Hall switch is also reversed. The transistor output is generally used at the output end. Similar to the proximity switches, there are NPN, PNP, normally open, normally closed, latched (bipolar), and dual signal outputs. Hall switch has the characteristics of no electric shock, low power consumption, long service life, high response frequency, etc. The internal use of epoxy sealing and integration, so it can work reliably in all kinds of harsh environments. Hall switches can be applied to proximity switches, pressure switches, odometers, etc. as a new type of electrical accessories.

Second, the internal schematic

Proximity switch classification and structure

The function of the proximity switch is to send a signal when an object approaches the proximity switch and reaches a certain distance. It does not require the application of external force, is a non-contact main commander. Its use has far exceeded the trip control and limit protection provided by the trip switch. Proximity switches can be used for high-speed counting, detection of the presence of metal bodies, speed measurement, level control, detection of part sizes, and use as contactless buttons. At present, the widely used proximity switches can be divided into the following types based on the working principle:

High-frequency oscillation type: used to detect various metal bodies

Capacitance type: used to detect various conductive or non-conductive liquids or solids

Photoelectric type: used to detect all opaque substances

Ultrasonic type: used to detect substances that do not transmit ultrasonic waves

Electromagnetic induction type: used to detect magnetic or non-magnetic metal

According to its shape, it can be divided into cylinder type, square type, channel type, perforation type and separation type. Cylindrical type is easy to install, but its detection characteristics are the same. The groove type detection part is inside the tank. It is used to detect the objects passing through the tank. The penetration type is rarely produced in our country, while in Japan it is more common and can be used. Small parts such as small screws or balls and buoys are assembled into water level detection devices.

Proximity switch can be divided into direct current type and alternating current type according to power supply. According to output type, it can be divided into direct current two-wire system, direct current three-wire system, direct current four-wire system, alternating current two-wire system and alternating current three-wire system.

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