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Proximity switch, also known as non-contact travel switch, in addition to being able to complete stroke control and limit protection, is still a non-contact detection device, used to detect the size of parts and speed measurement, etc., and can also be used for frequency conversion counters, frequency conversion pulse generators, liquid level control and active connection of processing programs. It is characterized by reliable work, long life, low power consumption, high complex positioning accuracy, high operating frequency and harsh working environment.
Functional characteristics Among the various types of switches, there is a component that has the ability to "sense" the object approaching it - the displacement sensor. The proximity switch is used to use the sensitivity of the displacement sensor to the approaching object to achieve the purpose of controlling the switch on or off. Proximity switch When an object moves towards the proximity switch and approaches a certain distance, the displacement sensor will "perceive" and the switch will act. This distance is generally called the "detection distance". Different proximity switches have different detection distances. Sometimes the inspected objects are moved to the proximity switch one by one according to a certain time distance, and then leave one by one, and so on and so forth. Different proximity switches respond differently to the detected target. This echoing property is known as the "echo frequency". Because displacement sensors can be made according to different principles and different methods, and different displacement sensors have different methods of "perception" of objects, so the common proximity switches are as follows: 1. Eddy current proximity switch This type of switch is sometimes called an inductive proximity switch. It uses a conductive object to cause eddy currents to occur inside the object when approaching the proximity switch that can generate an electromagnetic field. This eddy current reacts to the proximity switch, causing the internal circuit parameters of the switch to change, so as to identify whether a conductive object is moving closer, so as to control the switch on or off. The object that can be detected by the proximity switch must be a conductor. 2. Capacitive proximity switch This type of switch is generally measured by one plate that makes up 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 the measurement process. When an object moves towards the proximity switch, regardless of whether it is a conductor or not, the dielectric constant of the capacitor must be changed due to its proximity, so that the capacitance is changed, so that the circuit condition connected to the measuring head is also changed, so that the switch can be turned on or off. The target of this proximity switch detection is not limited to conductors, liquids or powders that can be insulated. 3. Hall proximity switch A Hall element is a magnetic-sensitive element. Switches made of Hall elements are called Hall switches. When a magnetic object moves close to the Hall switch, the Hall element on the detection surface of the switch changes the internal circuit condition of the switch due to the Hall effect, so as to identify the presence of magnetic objects around it, so as to control the switch on or off. The object of the proximity switch must be a magnetic object. 4. Photoelectric proximity switch Switches made using the photoelectric effect are called photoelectric switches. The light-emitting equipment and the photoelectric equipment are installed in a unified detection head in a certain direction. When a reflective surface (the object to be detected) is approaching, the photoelectric device receives the reflected light and outputs it in the signal, so that it can "sense" the approach of the object. 5. Pyroelectric proximity switch Switches made with components that can sense temperature changes are called pyroelectric proximity switches. This kind of switch is to install the pyroelectric device on the detection surface of the switch, and when an object with a different temperature from the ambient is approaching, the output of the pyroelectric device is changed, so that an object can be detected. 6. Other types of proximity switches When the distance of the observer or system to the wave source changes, the frequency of the approaching wave shifts, a phenomenon called the Doppler effect. Sonar and radar are made using the principle of this effect. The Doppler effect can be used to make ultrasonic proximity switches, microwave proximity switches, etc. When an object moves closer, the reflected signal received by the proximity switch is Doppler-shifted, which makes it possible to identify the presence or absence of an object.
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