Performance characteristics and classification of

Performance characteristics and classification of proximity switch

proximity switch is a position switch that can be operated without direct mechanical contact with moving parts. When an object approaches the sensing surface of the switch to the action distance, the switch can act without mechanical contact and applying any pressure, so as to drive DC appliances or provide control instructions to computer (PLC) devices. Proximity switch is a kind of switch type sensor (i.e. contactless switch). It has the characteristics of travel switch and microswitch, and has sensing performance at the same time. It has reliable action, stable performance, fast frequency response, long service life, strong anti-interference ability, and has the characteristics of waterproof, shockproof, corrosion resistance, etc. The products are inductive, capacitive, hall, AC and DC

performance characteristics

among all kinds of switches, there is a kind of element that has the ability to "perceive" objects close to it - displacement sensor. The purpose of controlling the switch on or off is to use the sensitive characteristics of the displacement sensor to the approaching object, which is called the proximity switch

when an object moves to the proximity switch and approaches a certain distance, the displacement sensor will have "perception" and the switch will act. This distance is usually called "detection distance". However, the detection distance of different proximity switches is also different

sometimes the tested objects move to the proximity switch one by one and leave one by one at a certain time interval, which is repeated constantly. Different proximity switches have different response ability to the detected object. This response characteristic is called "response frequency"

classification

because displacement sensors can be made according to different principles and different methods, with an increase of about 8% compared with 2015, and different displacement sensors have different methods of "sensing" objects, there are the following common proximity switches:

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 closure. 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 currents inside the object when it approaches the proximity switch that can generate electromagnetic fields. This eddy current reacts on the proximity switch, changing 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 and processed by the rear pole and then converted into transistor on-off signal output [1]

2. Features: A. good anti-interference performance, high switching frequency, greater than 200Hz B. 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 kind of switch is usually a pole plate constituting the capacitor. On the one hand, they are increasingly involved in the development process of new products and new processes, and the other pole plate is the shell of the switch. The bus seat with memory cotton is comfortable and ergonomic. The shell is usually grounded or connected with the shell of the equipment during the measurement process. When an object moves to the proximity switch, whether it is a conductor or not, due to its proximity, the dielectric constant of the capacitance will always change, so that the capacitance will change, and the circuit state connected to the measuring head will also change, so that the connection or disconnection of the switch can be controlled. The objects detected by this proximity switch are not limited to conductors, insulating liquids or powders, etc

hall proximity switch

Hall element is a kind of magnetic sensor. The switch made of Hall element is called Hall switch. When the magnetic object moves close to the hall switch, the hall element on the detection surface of the switch changes the internal circuit state of the switch due to the Hall effect, so as to identify the presence of nearby magnetic objects, and then control the on or off of the switch. The detection object of this proximity switch must be a magnetic object

photoelectric proximity switch

the switch made of photoelectric effect is called photoelectric switch. Install the light-emitting device and the photoelectric device in the same detection head in a certain direction. When a reflective surface (detected object) approaches, the photoelectric device will output the signal after receiving the reflected light, so as to "perceive" the approaching of an object

other types

when the distance of the observer or system to the wave source changes, the frequency of the approaching wave will shift, which is called Doppler effect. Sonar and radar are made by using the principle of this effect. Ultrasonic proximity switch and microwave proximity switch can be made by using Doppler effect. When an object moves closer, the reflected signal received by the proximity switch will produce Doppler frequency shift, which can identify whether there is an object approaching

at the same time, proximity switch, also known as contactless proximity switch, is an ideal electronic switching value sensor. When the metal detector is close to the sensing area of the switch, the switch can quickly send out electrical instructions without contact, pressure and spark, and accurately reflect the position and stroke of the moving mechanism. Even for general stroke control, their project team has now settled in the science and service huizhongchuang space under the Provincial Department of science and technology, with its positioning accuracy, operation frequency, service life, convenience of installation and adjustment, and adaptability to harsh environments, It is incomparable to the general mechanical travel switch. It is widely used in machine tools, metallurgy, chemical industry, textile and printing industries. In the automatic control system, it can be used as limit, counting, positioning control and automatic protection links