About Introduction to proximity switches：
Proximity switch is a position switch that does not need to be operated by mechanical direct contact with moving parts. When the object is close to the switch sensing surface to the operating distance, the switch can be operated, so as to drive the DC electrical apparatus or provide control instructions to the computer (plc) device. Proximity switch is a switch type sensor (that is, contactless switch), it has the characteristics of stroke switch, micro switch, and sensing performance, and reliable action, stable performance, fast frequency response, long application life, strong anti-interference ability, and waterproof, corrosion resistance and other characteristics. Products are inductive, capacitive, Hall, AC, DC type.
Proximity switch, also known as contactless proximity switch, is an ideal electronic switching sensor. When the metal detector is close to the sensing area of the switch, the switch can be non-contact, no pressure, no spark, issue electrical instructions, accurately reflect the position and stroke of the moving mechanism, even for general stroke control, its positioning accuracy, operating frequency, service life, convenience of installation and adjustment and the ability to apply to harsh environments, is not comparable to the general mechanical stroke switch. Widely used in machine tools, metallurgy, chemical, textile and printing industries. In the automatic control system can be used as limit, counting, positioning control and automatic protection link.
Performance characteristics of proximity switches：
Among the various types of switches, there is a component that has the ability to "sense" the object close to it - the displacement sensor. Using the sensitive characteristics of the displacement sensor to the approaching object to control the switch on or off, this is the proximity switch.
When an object moves toward the proximity switch and is close to a certain distance, the displacement sensor has "perception" and the switch will act. This distance is usually called the "detection distance". But different proximity switches have different detection distances.
Sometimes the detected objects move toward the approach switch one by one and leave one by one at a certain time interval, so that they are repeated constantly. Different proximity switches have different response ability to detected objects. This response characteristic is called the "response frequency".
Type of proximity switch：
Because displacement sensors can be made according to different principles and different methods, and different displacement sensors have different "perception" methods of objects, there are the following common proximity switches:
Passive proximity switch
This switch does not require a power supply, and the closed state of the switch is controlled by magnetic induction. When the magnetic or iron trigger is near the switching magnetic field, the magnetic force inside the switch controls the closure. Features: No power required, non-contact, maintenance-free, environmental protection
Vortex access switch
This 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, which can generate an electromagnetic field. This eddy current reacts to the proximity switch, changes the internal circuit parameters of the switch, thereby identifying whether there is a conductive object moving closer, and then controls the switch on or off. The object that the proximity switch can detect must be an electrical conductor.
1. Principle: An oscillator composed of inductors and capacitors and transistors, and generate an alternating magnetic field, when a metal object is close to the magnetic field, it will produce eddy currents in the metal body, resulting in the oscillation to stop, and this change is amplified by the rear pole and converted into a transistor switching signal output.
2. Features: A, good anti-interference performance, high switching frequency, more than 200HZ.B, can only sense metal
3. Used in various mechanical equipment for position detection, counting signal picking, etc.
Capacitive proximity switch
The measurement of this switch is usually one plate that constitutes the capacitor, and the other plate is the housing of the switch. This housing is usually grounded or connected to the housing of the device during measurement. When an object moves toward the approach switch, regardless of whether it is a conductor, due to its proximity, the dielectric constant of the capacitor must change, so that the capacitance changes, so that the state of the circuit connected to the measuring head also changes, and the switch can be controlled to be switched on or off. The objects detected by this proximity switch are not limited to conductors, liquids or powders that can be insulated.
Photoelectric proximity switch
The switch made by photoelectric effect is called photoelectric switch. The light-emitting device and the photoelectric device are installed in the same detection head in a certain direction. When a reflective surface (detected object) approaches, the photoelectric device receives the reflected light and outputs it in the signal, thus it can "sense" that an object is approaching.
