Problems needing attention in the application of t

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Problems to be noticed in the application of proximity switch

proximity switch is also called contactless travel switch. In addition to completing travel control and limit protection, it is also a non-contact detection device, which is used to detect the size and speed of parts, as well as frequency conversion counter, frequency conversion pulse generator, liquid level control and automatic connection of processing programs. It is characterized by reliable operation, long service life, low power consumption, high complex positioning accuracy, high operation frequency and adaptability to harsh working environment

I. performance characteristics of proximity switch

among all kinds of switches, there is an element with "sensing" ability to approach other objects - displacement sensor. The purpose of controlling the switch on or off is to use the sensitive characteristics of the displacement sensor to the approaching object, which is called the proximity switch

when an object moves to the proximity switch and approaches a certain distance, the displacement sensor will have "perception" and the switch will act. This distance is usually called "detection distance". The detection distance of different proximity switches is not satisfactory

sometimes the tested objects move to the proximity switch one by one and leave one by one at a certain time interval, which is repeated constantly. Different proximity switches have different response ability to the detected object. This response characteristic is called "response frequency". Don't let your work be hindered

1 the action distance of the proximity switch

1) the action distance of the proximity switch is related to the material of the tested body. Under the same thickness and sensing area, the relationship between the action distance is s Iron>s stainless steel>s brass>s aluminum>s copper

2) the action distance of the proximity switch is related to the thickness and area of the tested body (when the material of the tested body is the same)

2 installation of proximity switch

1) a certain space should be reserved when installing the proximity switch on the metal to avoid the misoperation of the switch due to the interference of other metals other than the detected object. The metal parallel to the sensing surface shall be outside the detection distance of three times from the sensing surface, and the metal around the axis direction of the proximity switch shall be outside the cylinder with the axis of the proximity switch as the center and the diameter of three times the diameter of the proximity switch as the diameter

2) when installing two or more proximity switches at the same time, in order to prevent any interference between them, the distance between the two sensing surfaces in the axis direction should be greater than five times the detection distance. When installing in parallel, the distance between the outer cylindrical surfaces should be greater than three times the length of the proximity switch diameter. If the switch diameters are different, it should be calculated according to the diameter of the larger proximity switch

3 precautions during use

1) the tested body should not contact the proximity switch to avoid damage to the proximity switch due to friction and collision

2) pulling the lead of the proximity switch by hand will damage the proximity switch. During installation, it is best to firmly fix the lead at a distance of 10 cm from the switch with a wire clip

3) the new 3D sprint 2.5 should not be used to provide breakthrough productivity to step on the proximity switch, During installation, it is best to set a protective cover

4) the use distance of the switch should be set within 2/3 of the rated distance to avoid being affected by temperature and voltage, which will affect the sensitivity of the proximity switch

4 problems that should be paid attention to in wiring and wiring

1) the power line and power line should be as far away from the lead of the proximity switch as possible. When it is unavoidable, the electric metal tube should be sleeved outside and grounded to prevent the switch from damage or misoperation

2) it is strictly prohibited to connect the power line, and the wiring should be carried out according to the wiring output circuit schematic diagram

3) it is best not to use the output line of two proximity switches to control the same coil of the same relay, Otherwise, the source of the action will not be recognized, and sometimes even misoperation will occur

II. Main uses of proximity switches

proximity switches are widely used in aviation, aviation, aerospace technology and industrial production. In daily life, such as hotels, restaurants, garage automatic doors, automatic hot air machines are used. In terms of security and anti-theft, important places such as data archives, accounting, finance, museums, vaults and so on are usually equipped with anti-theft devices composed of various proximity switches. In measurement technology, such as length and position measurement; In the control technology, such as the measurement and control of displacement, velocity and acceleration, a large number of proximity switches are also used

III. precautions for the selection of proximity switches

in general industrial production sites, eddy current proximity switches and capacitive proximity switches are usually selected. Because these two proximity switches have low environmental requirements. When the measured object is a conductive object or an object that can be fixed on a metal object, eddy current proximity switches are generally selected because of its high response frequency, good anti-environmental interference performance, wide application range and low price. If the measured object is non-metal (or metal), liquid level height, powder height, plastic, tobacco, etc. Capacitive proximity switches should be used. This kind of switch has low response frequency but good stability. The influence of environmental factors should be considered during installation. If the object is a magnetic material or the magnetic steel is buried in the object to be measured in order to distinguish the object moving with it, hall proximity switch should be used instead of glass and metal switch, and its price is the lowest. (end)

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