Proximity Switches trip, also known as non-contact switch, which can be completed in addition to control and limit travel outside the protection of, or a non-contact type detection device for detecting the size and gun parts, etc. can also be used for frequency counters, frequency pulse generator, level control and automatic processes such as convergence. Characteristics of the work of a reliable, long life, low power consumption, complex and high precision positioning, high operating frequency, as well as to adapt to poor working environment.
First, the performance characteristics
In various types of switches, there is a thing of the close of its "perceived" ability components - displacement sensor. The use of displacement sensors close to objects to achieve the sensitivity control switch or pass off the end, which is close to switching.
When objects move close to switch, and close to a certain distance, the displacement sensor is "perception" will switch action. This distance is usually called the "detection distance." Proximity switch detecting different distances are also different.
Sometimes be detected by the inspection object is a certain time interval, one after another to move closer to switching, but also to leave one by one, so that repeat continuously. Close to a different switch, the response of the detection ability of the target are different. Response characteristics such as "frequency response."
Second: Type
Because the displacement sensor can be based on different principles and different ways to make the different objects of the displacement sensor on the "perceived" different ways, so close to common switches are as follows:
1, eddy current proximity switches
This switch is sometimes also called the Inductive Proximity Switch. It is the use of conductive objects near the electromagnetic field can produce close to the switch, so that eddy current generated objects. Close to the eddy current reaction to the switch, so switching to change the internal circuit parameters, which identify any conductive object closer to, and control of the pass or off switch. This switch can be detected close to the object must be electrical conductors.
2, Capacitive Proximity Switches
This switch is usually constitute a measurement of a plate capacitor, while the other is to switch the shell plate. The shell is usually in the measurement process and equipment is grounded or connected to the chassis. When objects move close to the switch, whether or not it is for the conductor, because of its proximity, the total capacitance of the dielectric constant to change, so that changes in capacity, making and measuring circuit connected to the first state also occurred changes, which can control access to or disconnect switches. Detection of such a switch close to the object, not limited to, the conductors can be insulated, such as liquid or powder.
3, Hall Proximity Switches
Hall element is a magnetic component. Hall element made of the use of switches, called the Hall switch. When the object moved closer to the Hall magnetic switch, the switch testing the surface because of the Hall element Hall-effect generated by the internal circuit switching changes in the state, which identify the existence of near magnetic objects, then control the pass or off switch. Detection of such a switch close to the target object must be magnetic.
4, Photoelectric Proximity Switches
Made use of the photoelectric effect is called photoelectric switch switch. The light-emitting devices and optoelectronic devices installed in a certain direction of the first in testing the same. When a reflective surface (detected objects) close to each other, optoelectronic devices after receiving the reflected light in the signal output, which can be "perceived" objects are closer.
5, pyroelectric Proximity Switches
Used to perceive changes in temperature caused by switching components called pyroelectric proximity switches. This switch is a piece of electrical pyroelectric detection switch installed on the surface, when the ambient temperature and close to different objects, the pyroelectric output electrical items will change, which can detect objects close to there.
6, other types of Proximity Switches
When the observer or the system changes the distance between wave source, the closer to the wave frequency shift will occur, a phenomenon called the Doppler effect. Sonar and radar is the use made of the effect of the principle. Doppler effect can be made of the use of ultrasound proximity switches, proximity switches, such as microwave. Closer to the time when there are objects close to switch to receive the reflected signals to produce Doppler frequency shift, which can be identified close to any object.
Third: the main purpose
Proximity Switches in aviation, aviation, space technology and industrial production have a wide range of applications. In their daily lives, such as hotels, restaurants, automatic garage doors have automatic hot application. In the security anti-theft devices, such as data files, accounting, finance, museum, treasury and other important place, usually equipped with a switch from close to the composition of the various anti-theft devices. In measurement techniques, such as length, location of measurement; in control technology, such as displacement, velocity, acceleration measurement and control, are also close to the use of a large number of switches.
Fourth, choose Notes
In general industrial production sites, usually close to selection of eddy current type proximity switches and capacitance switches. Because the two switches on the environment close to the lower requirements. When the measured object is conductive or may be fixed on a piece of metal object, eddy current type is generally chosen close to switch, because of its high frequency response, anti-interference performance of the environment, and the application of a wide range of lower prices. If the test is non-metallic (or metal), a high level, high powder, plastics, tobacco. Capacitor should be selected near the switch. This low-frequency response switch, but good stability.Installation should be taken into account the impact of environmental factors. If the material for the magnetic material or to the distinction and its movement in the objects with which the magnet inside the measured object buried in, the Hall should be used close to switch, it is the lowest price.
Better environmental conditions, no dust pollution of the occasion, to be used in photoelectric proximity switches. Photoelectric Proximity Switches work on the test object is almost no impact. So, as far as the fax machine on high, both in the tobacco machinery is widely used.
In the anti-theft system, automatic doors used pyroelectric Proximity Switches, Ultrasonic Proximity Switches, Proximity Switches microwave. Sometimes in order to enhance the reliability of identification, the number of switches are often close to the use of composites.
Regardless of choice of close to switch, should pay attention to the working voltage, load current, in response to the frequency of the various indicators, such as detection distance requirements. |
