The linear displacement sensor is a kind of electrical parameter sensor which was used earlier. It has complex types, low price and wide uses. Its basic principle is to convert the measured physical quantity into related resistance value, and then reflect the measured change through the corresponding measuring circuit. The sensor has simple structure, good linear accuracy and stable function, and can form an observation system for measuring force, weight, displacement and acceleration with the corresponding measuring circuit, which has become one of the indispensable methods for observing the production process and ending production automation.
2. Magnetoelastic displacement sensor
Magnetoelastic displacement sensor is composed of stainless steel (measuring rod), magnetoelastic wire (movable element-waveguide), movable float (with durable magnet inside) and so on. When the measuring rod magnetoelastic level gauge works, some circuits will excite pulse current on the waveguide wire. When the current is transmitted along the waveguide wire, a pulse current magnetic levitation field will be generated around the waveguide wire. There is a float outside the measuring rod of magnetoelastic liquid level meter, which can move up and down along the measuring rod with the change of liquid level. There is a set of durable magnetic rings in the float. When the pulse current magnetic field meets the magnetic field generated by the float, the magnetic field around the float becomes a pulse current magnetic field, and then the waveguide wire made of magnetoelastic material generates a modified wave pulse at the address of the float, which is transmitted back at a fixed speed along the waveguide wire. By measuring the time difference between the pulse current and the correction wave, the position of the float address, that is, the direction of the liquid level, can be accurately determined. The surface consists of a circuit unit, an explosion-proof shell and a rod-shaped sensor element. There are many types of sensors to choose from.
What are the commonly used displacement sensors? Types of displacement sensors
3.LVDT displacement sensor
LVDT displacement sensor is based on the principle of transformer. Through the weak electromagnetic coupling between the primary coil and the secondary coil, the displacement change of the iron core has an accurate linear relationship with the change of the output electrical signal (voltage or current), and the mechanical change can be directly converted into a standard electrical signal for computer data acquisition or PLC process control. LVDT displacement sensor product is based on the sensing coil and electronic circuit equipment in stainless steel tube, which has completed electromechanical integration and has strong anti-interference ability. This series of products has the advantages of long stroke, high precision, good stability and convenient use of equipment. It is a very powerful thing to view and analyze physical quantities such as displacement, distance, elongation, movement, thickness, vibration, expansion, liquid level, contraction and strain.
4. Pull rope displacement sensor
Rope displacement sensor is also called rope sensor. It is a new and concise length displacement sensor, which is widely used and has the advantages of compact structure, long measuring stroke, small equipment space standard, high measuring accuracy, good reliability, long service life and less maintenance. In addition, the cable displacement sensor equipment is convenient to use, suitable for many dangerous occasions and widely used in the field of measurement.
5. Grid displacement sensor
Grating displacement sensor (commonly known as grating ruler) is a measuring response device that works by using the optical principle of grating. Grating displacement sensor is often used in machine tools, current machining bases and measuring instruments, and can be used to view linear displacement or angular displacement. The measured output signal is a digital pulse, which has the characteristics of large viewing plane, high viewing accuracy and fast reference speed. For example, in CNC machine tools, it is often used to check the coordinates of the workpiece to investigate and track the feed failure, so as to compensate the motion failure.
According to the movement mode classification:
Linear displacement sensor: The function of linear displacement sensor is to convert linear mechanical displacement into electrical signal. #FormaTImgID_0# displacement sensor (Figure 8) In order to achieve this effect, the variable resistance slide rail is usually fixed at the fixed position of the sensor, and different resistance values are measured by the displacement of the slider on the slide rail. The sensor slide rail is connected to a stable DC voltage, allowing a small current of microamperes to pass through. The voltage between the slider and the starting end is proportional to the moving length of the slider. Using the sensor as a voltage divider can minimize the requirement for the accuracy of the total resistance of the slide rail, because the resistance change caused by temperature change will not affect the measurement results.
Angular displacement sensor: Angular displacement sensor is used to deal with obstacles: you can indirectly find obstacles by controlling your wheels with an angle sensor. The principle is simple: if the motor angle sensor works and the gear does not turn, it means that your machine is blocked by an obstacle. This technology is very simple to use and very effective; The only requirement is that the moving wheel can't slip on the floor (or slip too many times), otherwise you can't detect obstacles. This problem can be avoided by connecting an idler to the motor. This wheel is not driven by a motor, but by the movement of the device: if the idler wheel stops during the rotation of the driving wheel, it means that you have encountered an obstacle.
According to the material classification:
Hall-type displacement sensor: Its measuring principle is to keep the excitation current of Hall element (see semiconductor magnetic sensor) constant and make it move in a uniform gradient magnetic field, so the displacement of movement is proportional to the output Hall potential. The greater the magnetic field gradient, the higher the sensitivity; The more uniform the gradient, the more linear the relationship between Hall potential and displacement. Figure 2 shows three kinds of magnetic systems that generate gradient magnetic fields: system A has a narrow linear range, and when the displacement Z=0, the Hall potential is ≠ 0; System B has good linearity when z is 2mm, and Hall potential is 0 when Z=0. C system has high sensitivity, and the measuring range is less than 65438 0 mm. In the figure, n and s represent positive and negative magnetic poles respectively. Hall displacement sensor has the advantages of small inertia, high frequency response, reliable operation and long service life, so it is often used in various occasions where non-electric quantity is converted into displacement and then measured.
Photoelectric displacement sensor: measure the displacement or geometric size of the object according to the amount of luminous flux blocked by the measured object. It is characterized by non-contact measurement and continuous measurement. Photoelectric displacement sensor is often used to measure the diameter of wire continuously or as an edge position sensor in the edge position control system of strip steel.