Introduction of Inductive Proximity Switch Sensors

The inductive proximity switch is a low-cost method for non-contact detection of metal objects. When the metal object moves toward or backward of the proximity switch, the signal will automatically change to achieve the purpose of detection. Its composition is mainly composed of three parts: amplifying output circuit, switching circuit, oscillator. This article China PCB manufacturer-SysPCB has collected and sorted out some information, hoping to have a relatively large reference value for readers.
inductive proximity switch 

Working principle of inductive proximity switch
An oscillator, one of the three components of an inductive proximity switch, generates an alternating magnetic field. When the metal object approaches this magnetic field and reaches the sensing distance, an eddy current will be generated in the metal object, which will cause the oscillation to decay and even stop the vibration. The changes of oscillation are processed by the post-amplifier circuit and converted into switching signals, which trigger the drive control device, so as to achieve the purpose of non-contact detection.

Inductive proximity switches do not need mechanical contact with moving parts, and the sensing surface can automatically sense the target action, thereby generating drive and direct commands.

Inductive proximity switches can be well used for general stroke control, and their service life, positioning accuracy, operating frequency, are ease of installation and adjustment, and applicability to harsh environments are unmatched by general mechanical switches. Therefore, it can be widely used in textile, machine tool, printing, metallurgy, chemical and other industries.

Features of Inductive Proximity Switches
Inductive proximity switches can realize long-distance transmission, recording, display and control functions of information, and are widely used in industrial automatic control systems. It mainly has the following characteristics:
(1) The structure is simple, the inductive proximity switch has no active electrical contacts, the operation is reliable, and the service life is long.

(2) With high sensitivity and resolution, it can measure the displacement of 0.01 microns, and its output signal, the sensitivity of the output voltage per millimeter of displacement can reach hundreds of millivolts.

(3) The linearity and repeatability are good, and the nonlinear error of the inductive proximity switch can reach 0.1% to 0.05% within a certain range.

Electrical Specifications of Inductive Proximity Switch Sensors
1. Working voltage: refers to the power supply voltage range of the inductive proximity switch sensor, within this range, the electrical performance and safe operation of the sensor can be guaranteed.

2. Working current: refers to the maximum load current when the inductive proximity switch sensor works continuously.

3. Voltage drop: refers to the voltage measured at both ends of the switch or at the output when the switch is turned on at the rated current,

4. No-load current: refers to the current consumed by the measured sensor itself when there is no load.

5. Residual current: refers to the current flowing through the load when the switch is disconnected.

6. Polarity protection: the protection function to prevent the wrong polarity of the power supply.

7. Short circuit protection: When the limit current is exceeded, the output will be closed or released periodically until the short circuit is cleared.

The inductive proximity switch has the advantages of simple structure, fast dynamic response and easy non-contact measurement, suitable for acid, alkali, chloride, organic solvent, liquid ammonia, carbon dioxide, polyvinyl chloride powder, ash and oil-water interface level measurement. At present, it has been widely used in metallurgy, petroleum, chemical industry, coal, cement, food and other industries.