What is the principle of a proximity switch? The principle and use of the proximity switch

1. The working principle of inductive proximity switch.

An inductive sensor consists of three parts: an oscillator, a switching circuit, and an amplified output circuit. The oscillator produces an alternating magnetic field.

When a metal target approaches this magnetic field and reaches a sensing distance, eddy currents are generated within the metal target, resulting in oscillatory attenuation and even vibration stopping. The changes in oscillator oscillation and stop vibration are processed by the post-amplification circuit and converted into switching signals, which trigger the drive control device to achieve the purpose of non-contact detection.

The working principle of capacitive proximity switches.

The sensing surface of a capacitive proximity switch consists of two coaxial metal electrodes, much like an "open" capacitor electrode, which form a capacitor and are connected in series in an RC oscillation circuit.

When the power supply is turned on, the RC oscillator does not oscillate, and when a target approaches the capacitor's electricity, the capacitor's capacity increases and the oscillator begins to oscillate. Through the processing of the post-stage circuit, the two signals of oscillation and oscillation are converted into switching signals, so as to detect the existence of objects. The sensor can detect metal objects, but also can detect non-metallic objects, the maximum action distance can be obtained for metal objects, the action distance for non-metallic objects is determined by the dielectric constant of the material, the larger the dielectric constant of the material, the greater the action distance can be obtained.

How Hall switches work.

Magnetic switches are proximity switches that respond (even through non-ferrous metals) to a permanent magnetic field. The operating distance is greater than that of the inductive proximity switch. The response curve is related to the direction of the permanent magnetic field.

When a target (permanent magnet or external magnetic field) is approached, the magnetic permeability of the coil core (the amount of inductance of the coil L is determined by it) decreases, the amount of inductance of the coil also decreases, and the Q value increases. The oscillator is excited to oscillate and the oscillation current increases.

When a magnetic target is approached, the current consumption of the magnetic sensor increases.

Advantages:--The sensor can be mounted on metal.

There are three common types of proximity switches: mechanical, electromagnetic induction and permanent magnet.

1. The mechanical proximity switch is when the object touches the contact rod of the proximity switch, the switch acts; Such as travel switches, touch switches, etc.

2. Electromagnetic inductive proximity switch is when the object is close to the switch, the oscillator in the switch causes frequency offset or stop vibration due to changes in the external environment, so that the switch acts; Such as inductive proximity switches, capacitive proximity switches, etc.

3. The permanent magnet proximity switch is to install a permanent magnet element on the object to be detected, and when the object is close to the switch, the magnetic field of the permanent magnet element makes the proximity switch act; Such as reed proximity switches, Hall proximity switches, etc.

Generally speaking, there are three common proximity switches: capacitive, inductive and Hall proximity switches.

Capacitive sensors can detect any object in a non-contact way. In contrast to inductive sensors, which can only detect metal objects, capacitive sensors can also detect non-metallic materials.

Inductive proximity sensors must detect metal materials.

Hall proximity switch is composed of Hall elements, which has the characteristics of low energy consumption, non-destructive and long life.

The proximity switch has a technical indicator for the detection distance or the operating distance of the switch. This parameter can be selected according to different applications. If the detection distance is uncertain and an approximate range is required, a proximity sensor is recommended.

There are three common proximity switches: capacitive, inductive and Hall proximity switches.

1. Capacitive sensor material.

2. Inductive approach to materials.

3. Hall proximity switch.

There are so many proximity switches, how do you choose?

How proximity switches work.

Proximity switchesThe principle and usage method are as follows:

A proximity switch is a position switch that does not require mechanical direct contact with moving parts.

When the object moves the proximity switch sensing surface to the operating distance, the switch can be actuated, thereby driving the load, which can be an intermediate relay.

Or PLC input points.

There are three main categories of proximity switches: inductive proximity switches, capacitive proximity switches, and magnetic proximity switches. Among them, the most commonly used in our work sites are inductive proximity switches.

Inductive proximity switches: The sensing head of an inductive proximity switch is an inductive coil with a ferrite core.

Only metal bodies can be detected. The oscillator generates an alternating magnetic field on the surface of the sensing head, and when a metal object approaches the sensing head, the internal action of the proximity switch is achieved, so as to achieve "on" and "off" control.

Capacitive proximity switch: The sensing head of a capacitive proximity switch is a circular flat electrode that forms a distributed capacitance with the ground wire of the oscillating circuit, which is capacitive when there is a conductor or other medium approaching the sensing head.

The oscillator stops oscillating and outputs an electrical signal through the shaping amplifier. Capacitive proximity sensors can inspect metals, non-metals, and liquids.

Magnetic proximity switch: Magnetic proximity switch mainly refers to Hall proximity switch, and its working principle is Hall effect.

When a magnetic object approaches the Hall switch.

, the state of the Hall proximity switch changes, e.g. from "on" to "off".

The principle and usage of the proximity switch are as follows:

First, the principle of proximity switch.

The proximity switch is a transistor non-contact travel switch, when the object reaches a predetermined position, the proximity switch (proximity switch sensing and action distance) that enters the detection distance, the switch can be contactless, no pressure, no spark, speed determination to send electrical indication and precise reaction mechanism Movement and positioning of the stroke, positioning accuracy, working frequency, life, etc. compared with the general mechanical limit switch.

Proximity switch is a kind of sensor, which has the characteristics of reliable performance, reliable action, stable performance, fast response speed, long service life, strong anti-interference ability, waterproof, impact resistance, corrosion resistance and so on.

Second, the use of proximity switches.

1. The ON state and OFF state of DC two-wire proximity switch are actually large and small changes in current, when the proximity switch is in the OFF state, there is still a small current through the load, when the proximity switch is in the ON state, there is a voltage drop of about 5V on the circuit, so the driving current and driving voltage on the control circuit must be considered in actual use to ensure the normal operation of the circuit.

2. When the DC three-wire system is connected in series, the sum of its voltage drop after series connection should be considered.

3. If there is a high voltage or power line near the sensor cable, the cable of the sensor should be installed separately into the metal conduit to prevent interference.

4. When using a two-wire sensor, when connecting the power supply, it is necessary to make sure that the sensor is connected to the power supply after the load to avoid damage to the internal components. When the load current < 3mA, in order to ensure reliable operation, it is necessary to connect the false load.

Selection of proximity switches

1. Selection of proximity switch type.

The first choice is inductive type for detecting metal, the capacitive type is preferred for detecting non-metal, and the magnetic inductive proximity switch is used for detecting magnetic signals.

2. The choice of the appearance of the proximity switch.

Generally, the cylindrical thread shape is often selected, which can be selected according to actual needs.

3. Selection of detection distance.

According to the needs of the selection, the general manufacturer's manual will indicate the detection distance.

4. Signal output selection.

An AC proximity switch outputs an AC signal, while a DC proximity switch outputs a DC signal. Special note: The current of the load must be less than the output current of the proximity switch, otherwise a conversion circuit should be added.

5. Selection of switching frequency.

Switching frequency refers to the number of times a proximity switch transitions from "on" to "off" per second. The DC proximity switch can reach 200Hz, and the AC proximity switch can only reach 25Hz.

6. Selection of rated voltage.

AC proximity switches prefer AC 220V and AC 36V; DC 12V and DC 24V are preferred for DC proximity switches. In general, proximity switches have a wide range of voltage options.

Switches can be seen everywhere in our daily life, and the proximity switch is a position switch that can be operated without mechanical direct contact with moving parts, it is also known as a non-contact proximity switch, maybe you will feel very strange when you hear this name, but the proximity switch is widely used in our lives, such as in hotels, restaurants, garages on the automatic door, there are applications of proximity switches, so what is the working principle of the proximity switch?

There is a kind of element in the proximity switch that has the ability to "perceive" the object approaching it, that is, the displacement sensor, which can use the sensitive characteristics of the displacement sensor to the approaching object to achieve the purpose of controlling the switch on or off, and the distance perceived by the displacement sensor after the object moves to the switch and approaches to a certain distance is called the detection distance. Sometimes the detected object is repeated continuously after approaching the switch at a certain time interval and then leaving it one after another, and the response ability of different proximity switches to the detected object is also different chain early, which is called the response frequency.

2. What are the types of proximity switches?

1. Passive proximity switch is a non-contact switch that does not require power supply and is controlled by magnetic induction, which does not require maintenance and is environmentally friendly.

2. Eddy current proximity switch, also known as inductive proximity switch, is the use of conductive objects to produce eddy current inside the object when proximity switching, its anti-interference performance is good, and the switching frequency is high.

3. Capacitive proximity switch is a kind of proximity switch when an object moves to the proximity switch, regardless of whether it is a conductor or not, the dielectric constant of the capacitance can change, it is not limited to the conductor, and the insulating liquid or powder is its detection object.

4. The photoelectric proximity switch, also known as the photoelectric switch, is to install the luminaire and the photoelectric device in the same detection head in a certain direction, and the photoelectric device will output the signal after receiving the reflected light, so that it can perceive that there is an object approaching.

The above is for you to introduce the working principle and types of proximity switches, I hope to help you, understand the working principle and various types of proximity switches, for us to be able to provide a little help when purchasing proximity switches, there are many brands on the market, we should look at all kinds of brands when purchasing, shop around, and choose a good proximity switch through comparison.

When it comes to proximity switches, many people will not be unfamiliar, but if you really want to tell you why it is and accurately tell what the proximity switch is, it still confuses many people. Today, I will tell you what a proximity switch is.

What is a proximity switch.

Proximity switch is a position switch that can be operated without direct contact with the moving parts, when the object is close to the sensing surface of the switch to the action distance, it does not need mechanical contact and exerts any pressure to make the switch act, so as to drive DC electrical appliances or provide control instructions to computer (PLC) devices. Proximity switch is a kind of switch sensor (i.e., no contact switch), which not only has the characteristics of travel switch and micro switch, but also has the characteristics of sensing performance, reliable action, stable performance, fast frequency response, long application life, strong anti-interference ability, etc., and has the characteristics of waterproof, shockproof and corrosion-resistant.

According to its appearance, the proximity switch can be divided into cylindrical type, square type, groove type, perforated (through) type and separated type. The garden column type is easy to install than the square type, but its detection characteristics are the same, the detection part of the groove type is on the inside of the groove, which is used to detect the objects in the groove, and the through type is rarely produced in China, while Japan is more commonly used, which can be used for small parts such as small screws or balls and buoys assembled into water level detection devices.

Proximity switch principle.

Proximity switches are inductive, capacitive, Hall, AC and DC types. Proximity switches, also known as contactless proximity switches, are ideal electronic switching sensors. When the metal detector is close to the sensing area of the switch, the switch can be contactless, no pressure, no sparks, quickly issue electrical instructions, accurately reflect the position and stroke of the moving mechanism, even if it is used for general stroke control, its positioning accuracy, operation frequency, service life, convenience of installation and adjustment and adaptability to harsh environments are incomparable with general mechanical travel switches.

When an object moves towards the proximity switch and approaches a certain distance, the displacement sensor will sense and the switch will act. This distance is usually called the detection distance. However, different proximity switches have different detection distances.

Sometimes the objects to be inspected are moved to the proximity switch one by one at certain intervals, and then leave one by one, so that it is repeated without interruption. Different proximity switches have different responsiveness to the detected object. This response characteristic is known as the response frequency.

After reading the introduction of what a proximity switch is, do you have a comprehensive understanding of this product category?The broadening of knowledge about home life needs to be accumulated over time, and I hope that the explanation will bring guidance for everyone to learn more relevant knowledge.