是工业实践中最为常用的一种传感器，其广泛应用于各种工业自控环境，涉及水利水电、铁路交通、智能建筑、生产自控、航空航天、军工、石化、油井、电力、船舶、机床、管道等众多行业，下面就简单介绍一些常用压力变送器的原理及其应用、力学传感器的种类繁多，如电阻应变片压力变送器、半导体应变片压力变送器、压阻式压力变送器、电感式压力变送器、电容式压力变送器、谐振式压力变送器及电容式加速度传感器等。 Pressure transmitter is the most commonly used sensor in industrial practice. It is widely used in various industrial automatic control environments, including water conservancy and hydropower, railway transportation, intelligent buildings, production automatic control, aerospace, military, petrochemical, oil wells, electricity, ships , Machine tools, pipelines and many other industries, the following briefly introduces the principles and applications of some commonly used pressure transmitters, a wide range of mechanical sensors, such as resistance strain gauge pressure transmitters, semiconductor strain gauge pressure transmitters, piezoresistive Pressure transmitters, inductive pressure transmitters, capacitive pressure transmitters, resonant pressure transmitters, and capacitive acceleration sensors. But the most widely used is the piezoresistive pressure transmitter, which has a very low price and high accuracy and good linearity. Below we mainly introduce such sensors. In understanding the piezoresistive pressure transmitter, we first understand the element such as a resistance strain gauge. The resistance strain gauge is a sensitive device that converts the strain change on the DUT into an electrical signal. It is one of the main components of a piezoresistive strain transmitter. The most commonly used resistance strain gages are metal resistance strain gages and semiconductor strain gages. There are two types of metal resistance strain gauges: wire strain gauges and metal foil strain gauges. Usually, the strain gauge is tightly adhered to the substrate that generates mechanical strain through a special adhesive. When the substrate undergoes a stress change, the resistance strain gauge also deforms together, so that the resistance value of the strain gauge changes, so that The voltage applied to the resistor changes. Such strain gauges usually have small changes in resistance when subjected to force. Generally, these strain gauges form a strain bridge, which is amplified by subsequent instrumentation amplifiers and then transmitted to the processing circuit (usually A / D conversion). And CPU) display or actuator.
The internal structure of a metal resistance strain gauge is a schematic diagram of the structure of the resistance strain gauge, which is composed of a base material, a metal strain wire or a strain foil, an insulation protection sheet, and a lead wire. According to different purposes, the resistance value of the resistance strain gauge can be designed by the designer, but the value range of the resistance should be noted: the resistance value is too small, the required drive current is too large, and the heat of the strain gauge causes its own temperature to be too high , Used in different environments, the resistance value of the strain gauge changes too much, the output zero point drift is obvious, and the zeroing circuit is too complicated. The resistance is too high, the impedance is too high, and the ability to resist external electromagnetic interference is poor. Generally it is about several tens to several tens of thousands of ohms. Working principle of resistance strain gage The working principle of metal resistance strain gage is the phenomenon that the resistance changes with the mechanical deformation of the strain resistance absorbed on the base material, which is commonly known as the resistance strain effect. The resistance value of a metal conductor can be expressed by the following formula: In the formula: ρ-the specific resistance of the metal conductor (Ω? Cm2 / m)-the cross-sectional area of the conductor (cm2)-the length of the conductor (m) we use the wire strain As an example, when the wire is subjected to external force, its length and cross-sectional area will change. It can be easily seen from the above formula that its resistance value will change. If the wire is extended by the external force, As the length increases and the cross-sectional area decreases, the resistance value increases. When the metal wire is compressed by an external force, the length decreases and the cross section increases, and the resistance value decreases. As long as the change in resistance is measured (usually the voltage across the resistance), the strain condition of the strained wire,
原理及应用 2. Principle and application of ceramic pressure transmitter
The anti-corrosive pressure transmitter has no liquid transmission. The pressure directly acts on the front surface of the ceramic diaphragm, causing the membrane to deform slightly. The thick film resistor is printed on the back of the ceramic diaphragm and connected to form a Wheatstone bridge ( (Closed bridge), due to the piezoresistive effect of the varistor, the bridge generates a voltage signal that is highly linear and proportional to the pressure and proportional to the excitation voltage. The standard signal is calibrated to 2.0 / 3.0 / according to different pressure ranges. 3.3mV / V, etc., can be compatible with strain sensors. Through laser calibration, the sensor has high temperature stability and time stability. The sensor has a temperature compensation of 0 ～ 70 ℃, and can directly contact most media. Piezoelectric sensors are mainly used in the measurement of acceleration, pressure and force. A piezoelectric acceleration sensor is a commonly used accelerometer. It has the advantages of simple structure, small size, light weight and long service life. Piezoelectric acceleration sensors have been widely used in vibration and shock measurement of aircraft, automobiles, ships, bridges and buildings, especially in the aerospace and aerospace fields. Piezoelectric sensors can also be used to measure internal combustion pressure and vacuum. It can also be used in the military industry. For example, it can be used to measure the change in the bore pressure and the shock wave pressure of the muzzle when a gun bullet is fired in the bore. It can be used to measure both large and small pressures.
英文名称（Pressure Transmitter）一般意义上的压力变送器主要由测压元件传感器（也称作压力传感器）、测量电路和过程连接件三部分组成。 Pressure transmitter English name (Pressure Transmitter) In the general sense, a pressure transmitter is mainly composed of a load cell sensor (also called a pressure sensor), a measurement circuit and a process connection. It can convert the physical pressure parameters such as gas and liquid felt by the load cell sensor into standard electrical signals (such as 4 ~ 20mADC, etc.), and provide secondary indicators such as alarm indicators, recorders, and regulators for measurement and indication. And process regulation. When the pressure signal acts on the sensor, the pressure sensor converts the pressure signal into an electrical signal, which is amplified by differential amplification and output amplifier, and finally converted by V / A voltage and current into a linear correspondence with the liquid level pressure of the measured medium (liquid). 4-20mA standard current output signal.
Common pressure transmitter: 3051 pressure transmitter
Performance characteristics of pressure transmitter
Product image of pressure transmitter
Technical parameters of pressure transmitter
Application field of pressure transmitter
Application range of pressure transmitter
How to choose the right pressure transmitter