Application and working principle of human proximity sensor
Source: far Extension Technology Author: Shi Xinhua 1. Overview of the human body, also known as non-contact proximity sensor, proximity sensor, is the ideal electronic switch sensor. When the metal detection body approaches the sensing area of ​​the sensor, the switch can be contactless, without pressure, without sparks, and quickly send out electrical commands to accurately reflect the position and stroke of the motion mechanism. Even if it is used for general stroke control, its positioning accuracy and operation Frequency, service life, ease of installation and adjustment, and ability to adapt to harsh environments are incomparable to general mechanical limit switches. It is widely used in machine tool, metallurgy, chemical, textile and printing industries. It can be used as limit, count, positioning control and automatic protection in the automatic control system. The proximity sensor has the characteristics of long service life, reliable operation, high repeat positioning accuracy, no mechanical wear, no sparks, no noise, and strong vibration resistance. So far, the range of applications of proximity sensors has become increasingly widespread, and its own development and innovation has been extremely rapid.
The human body proximity sensor has been gradually recognized and applied as a technical defense method. In order to better implement the national standard of GB / T10488-1997 human proximity sensor, the smooth implementation of human proximity sensor makes more people understand the principle and application of human proximity sensor. Now the human proximity sensor developed and produced by Nanjing Yuantuo Technology introduces the principle of human proximity sensor And basic knowledge of application.
Application of human body proximity sensor in ATM cash machine monitoring:
ATM dedicated human body proximity sensor YTMW8631 and human activity monitor YT-EWS, a control device for detecting human body proximity can accurately detect the proximity of nearby people, and is currently the best choice as an alarm and status detection. The sensing part has a high detection sensitivity to the movement of accessory characters and a strong ability to interfere with the sound signal suppression of the surrounding environment. It can be widely used in anti-theft devices such as ATM insurance. It is easy to install and can be installed horizontally or vertically. The sensitivity to human body induction is continuously adjustable, which makes the human body proximity sensor suitable for many different occasions.
Widely used in financial industry and commerce, self-service banking, ATM monitoring human body proximity alarm, etc. The internal use of micro-circuit chip for program control processing has high detection sensitivity and trigger reliability. The detection and control are combined into one, with low waiting power consumption, switch signal output, and directly trigger alarm recording, which is easy to use.
Performance characteristics:
(1) With the function of penetrating walls and non-metallic doors and windows, it is suitable for concealed built-in installation of bank ATM monitoring system;
(2) The proximity of the detection human body is adjustable, and the adjustable radius is (approximately) 0-5 meters;
(3) The detection area is double fan-shaped, covering a large space;
(4) Double comparison of the amplitude and width of the detection signal, the false alarm is small;
(5) It has a high environmental temperature adaptability, and does not affect the detection sensitivity at -20 to 50 degrees Celsius.
(6) Non-contact detection.
(7) Not subject to temperature, humidity, noise, airflow, dust, light, etc. suitable for harsh environments.
(8) Strong resistance to radio frequency interference.
2. The classification and structure of Yuantuo's human proximity sensor 2.1 Two-wire proximity sensor Two-wire proximity sensor is simple to install and convenient to wire; it is widely used, but it has the disadvantages of large residual voltage and large leakage current.
2.2 DC three-wire type The output types of DC three-wire proximity sensors are NPN and PNP. In the 1970s, the vast majority of Japanese products were NPN output, and both NPN and PNP output types in Western European countries. PNP output proximity sensors are generally used in PLCs or computers as control commands. NPN output proximity sensors are used to control DC relays. In actual applications, the output form should be selected according to the characteristics of the control circuit.
3 Proximity sensor selection and detection 3.1 For different types of detection bodies and different detection distances, different types of proximity sensors should be selected to make them have a high performance-price ratio in the system. The following principles should be followed:
3.1.1 When the detection body is a metal material, a high-frequency oscillation type proximity sensor should be selected. This type of proximity sensor is most sensitive to the detection of iron-nickel and A3 steel detection bodies. For aluminum, brass and stainless steel samples, the detection sensitivity is low.
3.1.2 When the detection body is a non-metallic material, such as; wood, paper, plastic, glass, water, etc., a capacitive proximity sensor should be used.
3.1.3 When metal bodies and non-metals are to be detected and controlled at a distance, optoelectronic proximity sensors or ultrasonic proximity sensors should be used.
3.1.4 When the detection body is metal, if the detection sensitivity requirement is not high, a low-cost magnetic proximity sensor or Hall-type proximity sensor can be used.
3.2 Proximity sensor technical index detection 3.2.1 Action distance measurement; when the action piece approaches the sensing surface of the proximity sensor from the front, the proximity sensor action distance is the maximum action distance of the proximity sensor, and the measured data should be within the product parameter range Inside.
3.2.2 Determination of the release distance; when the action piece is away from the sensing surface of the proximity sensor from the front and the switch is switched from action to release, the maximum distance of the action piece from the sensing surface is measured.
3.2.3 Determination of the return difference H; the absolute value of the difference between the maximum operating distance and the release distance.
3.2.4 Determination of operating frequency; drive the bakelite disc with a speed-regulating motor, fix a number of steel plates on the disc, adjust the distance between the switch sensing surface and the operating plate, about 80% of the switching action distance, rotate the disc, In turn, move the action piece close to the proximity sensor. A speed measuring device is installed on the disc spindle. The output signal of the switch is shaped and connected to the digital frequency meter. At this time, the motor is started, and the speed is gradually increased. Under the condition that the product of the speed and the action piece is equal to the frequency count, the operating frequency of the switch can be directly read by the frequency meter.
3.2.5 Repeatability measurement; fix the action piece on the measuring tool, from 120% of the distance of the switch, from the front of the switch sensing surface to the action area of ​​the switch, the movement speed is controlled at 0.1mm / s When the switch is in action, read the reading on the gage and then exit the action area to make the switch open. Repeat this 10 times, and finally calculate the difference between the maximum and minimum values ​​of the 10 measurements and the average value of 10 times. The greater the difference is the repeat accuracy error.
What is the working principle of Yuantuo human proximity sensor?
â‘ There is a high frequency transmitter in the human proximity sensor, which will cause the coil to emit a high frequency magnetic field.
â‘¡ When the measured object is close to the high-frequency magnetic field, eddy current will be generated on the surface of the detected object, and the eddy current will cause a magnetic field in the opposite direction.
â‘¢ The transmitter is cancelled by the influence of the magnetic field generated by the eddy current to stop the vibration.
â‘£ Turn the control output ON / OFF according to the presence or absence of vibration.
Among all kinds of switches, there is an element that has the ability to "perceive" the objects approaching it-displacement sensors. Using the sensitive characteristics of the displacement sensor to approach objects to achieve the purpose of controlling the switch on or off, this is the proximity switch.
Because displacement sensors can be made according to different principles and different methods, and different displacement sensors have different methods of "perception" of objects, the common proximity switches are as follows:
Eddy current proximity switches, capacitive proximity switches, Hall proximity switches, photoelectric access switches, pyroelectric proximity switches, other types of proximity switches The main uses are:
Nanjing Yuantuo Technology's human body connection sensors and human activity monitors are widely used in bank ATM trigger monitoring video, aviation, aerospace technology, safes and industrial production. In daily life, such as automatic doors in hotels, restaurants, and garages, automatic hot fans are used. In terms of security and anti-theft, such as data files, accounting, finance, museums, vaults, etc., usually have anti-theft devices composed of various proximity switches. In the measurement technology, such as the measurement of length and position; in the control technology, such as the measurement and control of displacement, velocity, acceleration, a large number of proximity switches are also used.
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