Proximity switch, also known as non-contact travel switch, in addition to completing travel control and limit maintenance, is also a non-contact detection device, used to detect the size of parts and speed measurement, etc., can also be used for frequency conversion counter, frequency conversion pulse generator, liquid level control and automatic connection of processing programs. Having said so much, you may not be very familiar with it, today, Xiaobian will introduce you to the common types of proximity switches.
The characteristics of proximity switches include reliable operation, long life, low power consumption, high repositioning accuracy, high operating frequency and adaptation to harsh working environments. Since displacement sensors can be made according to different principles and different methods, and different displacement sensors have different methods of "perceiving" objects, the common proximity switches are as follows:
Common types of proximity switches: 1. Eddy current proximity switches This kind of switch is sometimes called inductive proximity switch. It is the application of a conductive object to produce eddy currents 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 there is a conductive object moving closer, and then control the switch on or off. The object that can be detected by the proximity switch must be a conductor.
Common types of proximity switches 2, capacitive proximity switches The measurement of this kind of switch is usually one plate that constitutes the capacitor, and the other plate is the shell of the switch. This enclosure is usually grounded or connected to the enclosure of the device during the measurement process. When an object moves towards the proximity switch, regardless of whether it is a conductor or not, due to its proximity, the dielectric constant of the capacitance must always change, so that the capacitance changes, so that the circuit state connected to the measuring head also changes, so that the switch can be switched on or off. This proximity switch detects not only conductors, but also liquids and powders that can be insulated.
Common types of proximity switches 3. Hall proximity switch 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 state of the internal circuit of the switch due to the Hall effect, so as to identify the existence of a magnetic object near the left, and then control the switch on or off. The object of detection of such a proximity switch must be a magnetic object.
Fourth, the switch made of photoelectric proximity switch using the photoelectric effect is called a photoelectric switch. The light-emitting device and the optoelectronic device are installed in the same detection head in a certain direction. When a reflective surface (the object to be detected) is approaching, the optoelectronic device receives the reflected light and outputs it in the signal, so that it can "sense" the approach of the object. Common types of proximity switches 5. Pyroelectric proximity switches are called pyroelectric proximity switches made of components that can sense temperature changes. This type of switch is to install a pyroelectric device on the detection surface of the switch, and when an object with a different temperature from the ambient approaches, the output of the pyroelectric device changes, so that an object can be detected.
When the observer or system changes the distance of the wave source, the frequency of the approaching wave will be shifted, which is called the Doppler effect. Sonar and radar are made by applying the principle of this effect. The application of Doppler effect can be made into ultrasonic proximity switches, microwave proximity switches, etc. When an object is approaching, the reflected signal received by the proximity switch generates a Doppler shift, which can identify the presence or absence of an object approaching.