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Pressure sensor related knowledge

source:HEYYEN Electronics (Shanghai) Co., Ltd.time:2019-08-28views:Loading...

  01, overview

  Pressure sensor is the most commonly used sensor in industrial practice. It is widely used in various industrial self-control environments, involving water conservancy and hydropower, railway transportation, intelligent building, production automation, aerospace, military, petrochemical, oil well, electric power, ship, machine tool. Pipes and many other industries, the following briefly introduces some common sensor principles and their applications. There is also a medical pressure sensor. A pressure transducer (Pressure Transducer) is a device or device that can sense a pressure signal and convert the pressure signal into a usable output electrical signal according to a certain rule. Pressure sensors are usually composed of pressure sensitive components and signal processing units. According to different test pressure types, pressure sensors can be divided into gauge pressure sensors, differential pressure sensors and absolute pressure sensors.

  02, principle

  1, piezoresistive force sensor

  The strain gauge is one of the main components of the piezoresistive strain sensor. The working principle of the metal resistance strain gauge is a phenomenon in which the strain resistance adsorbed on the base material changes with the mechanical deformation, which is commonly called the resistance strain effect.

  2, ceramic pressure sensor

  The ceramic pressure sensor is based on the piezoresistive effect. The pressure acts directly on the front surface of the ceramic diaphragm to cause a slight deformation of the diaphragm. The thick film resistor is printed on the back of the ceramic diaphragm and connected into a Wheatstone bridge due to the varistor. The piezoresistive effect causes the bridge to generate a highly linear voltage signal proportional to the pressure, which is proportional to the excitation voltage. The standard signal is calibrated to 2.0/3.0/3.3mV/V depending on the pressure range. The strain gauge sensor is compatible.

  3. Diffused silicon pressure sensor:

  The working principle of the diffused silicon pressure sensor is also based on the piezoresistive effect. Using the principle of piezoresistive effect, the pressure of the measured medium directly acts on the diaphragm of the sensor (stainless steel or ceramic), so that the diaphragm generates a micro-displacement proportional to the pressure of the medium. The resistance value of the sensor is changed, the change is detected by an electronic circuit, and a standard measurement signal corresponding to the pressure is converted and output.

  4, sapphire pressure sensor:

  Using strain-resistive operation, silicon-sapphire is used as a semiconductor sensor with unparalleled metrology. Therefore, semiconductor sensitive components made of silicon-sapphire are insensitive to temperature changes, and have excellent operating characteristics even under high temperature conditions; sapphire has extremely strong radiation resistance; in addition, silicon-sapphire semiconductor sensitive components, Pn drift.

  5, piezoelectric pressure sensor:

  The piezoelectric effect is the main working principle of the piezoelectric sensor. The piezoelectric sensor cannot be used for static measurement, because the electric charge after the external force is saved only when the loop has an infinite input impedance. This is not the case, so this determines that the piezoelectric sensor can only measure dynamic stresses.

  03, installation problem

  Install correctly

  Usually, the damage of the high temperature melt pressure sensor is caused by the improper installation position. If the sensor is forcibly installed in an excessively small hole or an irregular hole, the vibration film of the sensor may be damaged by the impact. Choosing the right tool to machine the mounting hole is beneficial to control the size of the mounting hole. In addition, the proper mounting torque is good for forming a good seal, but if the installation torque is too high, it will easily cause the high temperature melt pressure sensor to slip off, in order to prevent this. This occurs, usually by applying a release compound to the threaded portion of the sensor prior to installation.

  1. The correct installation method of the pressure sensor:

  (1) Verify the frequency response of the pressure sensor under normal atmospheric pressure and standard temperature conditions with appropriate instrumentation.

  (2) Verify the correctness of the pressure sensor's code and the corresponding frequency response signal.

  2. Determine the specific installation location

  In order to determine the number and specific installation position of the pressure sensor, it is necessary to consider each inflation section of the inflation net.

  (1) The pressure sensor must be installed along the cable, preferably at the cable connector.

  (2) There should be no less than 4 pressure sensors per cable, and two pressure sensors close to the telephone office should not be 200m apart.

  (3) Install one at the beginning and end of each cable.

  (4) One branch point should be installed for each cable. If the two branch points are close together (less than 100 m), only one can be installed.

  (5) 1 cable installation method (overhead, underground) should be installed

  (6) For cables without branches, because the cable program of the barrier is the same, the installation distance of the pressure sensor is not 500m, and the total number is not less than 4.

  (7) In order to facilitate the determination of the pressure sensor failure point, in addition to installing the pressure sensor at the starting point, from the starting point of 150~200m, it is necessary to install another one. Of course, in the design, economic and technical factors must be considered. Where the pressure sensor is located, it should not be installed.

  Check size

  If the size of the mounting hole is not suitable, the threaded portion of the high-temperature melt pressure sensor is easily worn during the installation process, which not only affects the sealing performance of the device, but also prevents the sensor from fully functioning and may even pose a safety hazard. . Only the proper mounting holes can avoid thread wear (Thread Industry Standard 1/2-20UNF2B). Mounting holes can usually be tested with a mounting hole gauge to make the appropriate adjustments.

  04, application field

  Pressure sensors are mainly used in: supercharger cylinders, superchargers, gas-liquid booster cylinders, gas-liquid boosters, presses, compressors, air-conditioning refrigeration equipment and other fields.

  1, applied to the hydraulic system

  The pressure sensor is mainly used in the hydraulic system to complete the closed-loop control of the force. When the control spool suddenly moves, a spike of several times the system operating pressure is formed in a very short time. In typical mobile machinery and industrial hydraulics, any pressure sensor can be destroyed quickly if it is not designed with such extreme conditions in mind. There is a need to use an impact-resistant pressure sensor. There are two main methods for achieving pressure resistance. One is a strain-change chip, and the other is an external coil. The first method is generally used in a hydraulic system, mainly because Easy to install. Another reason is that the pressure sensor is also subjected to uninterrupted pressure pulsations from the hydraulic pump.

  2. Applied to safety control system

  Pressure sensors are often used in safety control systems, mainly in the field of air compressors' own safety management systems. There are many sensor applications in the field of safety control. As a very common sensor, pressure sensors are not surprisingly used in safety control systems.

  In the field of safety control, the application is generally considered from the perspective of performance. From the consideration of price, and from the convenience of practical operation, it is proved that the effect of selecting a pressure sensor is very good. Pressure sensors use mechanical processing techniques to mount components and signal conditioners on a small chip. Therefore, small size is also one of its advantages, in addition, the price is also another big advantage. To a certain extent it can improve the accuracy of system testing. In the safety control system, the pressure exerted by the compressor is controlled to some extent by installing a pressure sensor in the piping of the air outlet, which is a certain protection measure and a very effective control system. When the compressor is started normally, if the pressure value does not reach the upper limit, the controller will open the air inlet and adjust to make the equipment reach the maximum power.

  3. Applied to injection mold

  Pressure sensors play an important role in injection molds. The pressure sensor can be installed in the nozzle of the injection molding machine, the hot runner system, the cold runner system and the cavity of the mold. It can measure the plastic from the nozzle of the injection molding machine during injection molding, filling, holding and cooling. Plastic pressure somewhere between the cavities.

  4. Applied to monitoring mine pressure

  Sensor technology is one of the key technologies for mine pressure monitoring. On the one hand, we should properly apply the existing sensors to serve the mining industry; on the other hand, as a sensor manufacturer, we must develop and develop new pressure sensors to adapt to more mining industry applications. There are many kinds of pressure sensors. Based on the special environment of mine pressure monitoring, mine pressure sensors mainly include: vibrating wire pressure sensor, semiconductor piezoresistive pressure sensor, metal strain gauge pressure sensor, differential transformer pressure sensor and so on. These sensors are used in a wide range of applications in the mining industry, depending on the specific mining environment.

  5. Applied to promote sleep

  The pressure sensor itself can't promote sleep. We just put the pressure sensor on the mattress. Because the pressure sensor has high sensitivity, when the person turns around, heartbeat and breathing, the sensor will analyze this series of information to infer sleep. What state is the person sleeping in, then through the analysis of the sensor, collecting the sensor's signal to get the sleep data such as heartbeat and breathing rhythm, and finally all the data processing into a piece of the track, of course, can compress your night's sleep into one The first few minutes of music.

  6. Applied to compressors, air conditioning equipment

  Pressure sensors are commonly used in air presses, as well as air conditioning and refrigeration equipment. These sensors are small in size and easy to install, and the pressure guiding port is usually designed with a special valve pin.

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