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Home > Other > Inductive proximity switch working principle Inductive proximity switc

Inductive proximity switch working principle Inductive proximity switch function

Published time: 2019-09-06

What is an inductive proximity switch?

Inductive proximity switches are a low-cost method for non-contact detection of metal objects. When a metal object moves toward or out of the proximity switch, the signal changes automatically to achieve the purpose of detection. Its composition is mainly composed of three parts: an amplified output circuit, a switching circuit, and an oscillator.

Its characteristics are: sturdy and compact; large sensing range; overload operation (65v dc or 320v ac/dc), and protection level, no matter how harsh the environment is; fast switching frequency; flexible installation, suitable for small Space; large working distance, can be used for welding applications, no reduction factor.

inductive proximity switch

Inductive proximity switch works

An oscillator of one of the three major components of an inductive proximity switch produces an alternating magnetic field. When the metal object approaches this magnetic field and reaches the sensing distance, it will generate eddy currents in the metal target, which will cause the oscillation to decay and even stop the vibration. The oscillation and oscillation of the oscillator are processed by the post-amplifier circuit and converted into a switching signal to trigger the drive control device to achieve the non-contact detection purpose.

The inductive proximity switch requires no mechanical contact with the moving parts, and the sensing surface can automatically sense the target action, thereby generating a drive and directly generating commands.

inductive proximity switch

The inductive proximity switch can be used well for general stroke control. Its service life, positioning accuracy, operating frequency, ease of installation and adjustment, and adaptability to harsh environments are incomparable with general mechanical switches. Therefore, it can be widely used in textile, machine tool, printing, metallurgy, chemical and other industries.

The role of inductive proximity switches

1. Detection distance

 The movement distance is the spatial distance from the reference position (the proximity surface of the proximity switch) to the reference position measured at the time of the switching operation to the detection surface when the detector moves in a certain manner. The rated action distance refers to the nominal value of the proximity switch action distance.

2. Set distance

 The distance that the proximity switch is set in the actual work, generally 0.8 times the rated action distance.

3. Return difference

The absolute value between the action distance and the reset distance.

4. Standard test body

 A metal test body that allows the proximity switch to be compared. The test body used by the factory is square A3 steel with a thickness of 1mm, and the side length used is 2.5 times that of the switch detection surface.

5. Output status

 divided into normally open and normally closed. When there is no detected object, the load of the normally open proximity switch is not operated due to the cutoff of the output transistor inside the proximity switch. When an object is detected, the transistor is turned on and the load is energized.

6. Detection method

sub-buried and non-buried. The embedded proximity switch is flush-mounted on the installation and can form the same surface as the mounted metal object. The non-buried proximity switch needs to expose the sensor head to achieve its long detection distance.

7. Response frequency 

 The number of times the switching action cycle is approached within a predetermined one second time interval.

Response time t: The difference between the time when the proximity switch detects the object time and the proximity switch occurs.

Formula can be converted by t=1/f

8. On-Phase Voltage Drop

The voltage drop across the output transistor in the switch when the switch is in the on state.

9. Output form

 divided into npn two lines, npn three lines, npn four lines, pnp two lines, pnp three lines, pnp four lines, DC two lines, AC two lines, AC five lines and other common form output.

 

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