官方微信

SEARCH

Submit
Cancel

NEWS

Focus on Right, share the wonderful moments of enterprises and exhibitions, popularize product technical knowledge, and answer frequently asked questions

/
/
/
Summary of strain gauge pressure sensor detection principles and construction

Summary of strain gauge pressure sensor detection principles and construction

(Summary description)Pressure sensors are one of the most commonly used sensors in industrial practice and are widely used in a variety of industrial self-control environments involving water conservancy and hydropower, railway transportation, intelligent construction, production self-control, aerospace, military, petrochemical, oil well, power, ship, machine tool, pipeline and many other industries. The following is a brief introduction to some common sensor principles and their applications.

Summary of strain gauge pressure sensor detection principles and construction

(Summary description)Pressure sensors are one of the most commonly used sensors in industrial practice and are widely used in a variety of industrial self-control environments involving water conservancy and hydropower, railway transportation, intelligent construction, production self-control, aerospace, military, petrochemical, oil well, power, ship, machine tool, pipeline and many other industries. The following is a brief introduction to some common sensor principles and their applications.

Information

Pressure sensors are one of the most commonly used sensors in industrial practice and are widely used in a variety of industrial self-control environments involving water conservancy and hydropower, railway transportation, intelligent construction, production self-control, aerospace, military, petrochemical, oil well, power, ship, machine tool, pipeline and many other industries. The following is a brief introduction to some common sensor principles and their applications.

 

There are many types of force sensors, such as resistance strain gauge pressure sensors, semiconductor strain gauge pressure sensors, piezoresistive pressure sensors, inductive pressure sensors, capacitive pressure sensors, resonant pressure sensors and capacitive acceleration sensors. However, the most widely used is the piezoresistive pressure sensor, which has a very low price, high accuracy and good linearity. In the following we focus on this type of sensor.

 

When learning about piezoresistive force sensors, we first meet the element of resistance strain gauges. A resistive strain gauge is a sensitive device that converts the strain change in the measured part into an electrical signal. It is one of the main components of a piezoresistive strain transducer. The two most used types of resistance strain gauges are metal resistance strain gauges and semiconductor strain gauges. There are two types of metal strain gauges: wire strain gauges and metal foil strain gauges. The strain gauges are usually bonded tightly to a mechanical strain-generating substrate by means of a special adhesive. When the substrate is subjected to stress changes, the strain gauges are deformed together, resulting in a change in the resistance of the strain gauges and thus in the voltage applied to the resistance. These strain gauges usually produce a small change in resistance when subjected to stress. Generally these strain gauges form a strain bridge and are amplified by a subsequent instrumentation amplifier and then transmitted to the processing circuit (usually A/D conversion and CPU) for display or actuation.

 

 

 

I. Strain gauge pressure sensors

 

1、Strain tube type

 

Also known as strain gauge. Its elastic sensitive element is a thin-walled cylinder closed at one end, the other end of which is flanged to the measured system. Two or four strain gauges are attached to the cylinder wall, half of which are attached to the solid part as temperature compensation gauges and the other half as measuring strain gauges. When there is no pressure, the four strain gauges form a balanced full bridge circuit; when pressure is applied to the inner cavity, the cylinder becomes "drum-shaped" and the bridge is unbalanced, resulting in a voltage output in relation to the pressure. This sensor can also use a piston to convert the measured pressure into a force to be transmitted to the strain relief cylinder or through a pendant chain shaped diaphragm to transmit the measured pressure. The strain barrel type pressure sensor is simple, easy to manufacture and highly applicable, and is widely used in dynamic pressure measurement of rockets, artillery shells and artillery.

 

2、Diaphragm type

 

Its elastic sensitive element is a round metal flat diaphragm fixed around the perimeter. When the diaphragm is deformed by pressure, the radial and tangential strains at the centre reach a positive maximum, while the radial strain at the edge reaches a negative maximum and the tangential strain is zero. For this reason, two strain gauges are often attached to the positive and negative maximum strains and connected into a half-bridge circuit with adjacent bridge arms to obtain greater sensitivity and temperature compensation. The use of circular foil strain gauges (see resistance strain gauges) makes maximum use of the strain effect of the diaphragm. The non-linearity of these sensors is more significant. The latest product of the diaphragm type pressure sensor is the role of the elastic sensitive element and the strain gauge set in a single crystal silicon diaphragm, that is, the use of integrated circuit process on the single crystal silicon diaphragm diffusion production resistance strip, and the use of the surrounding fixed structure made of solid-state pressure sensor (see piezoresistive sensor).

 

3、Strain beam type

 

When measuring smaller pressures, a fixed beam or a structure of equal strength beam can be used. One method is to use a diaphragm to convert the pressure into a force which is then transmitted to the strain beam via a force transmission rod. The maximum strain in the fixed beam at both ends in Figure 3 is at the ends and midpoints of the beam, where the strain gauges are attached. There are other forms of this structure, for example a suspended beam with a diaphragm or bellows can be used.

 

4. Combination type

 

In the combined strain pressure sensor, the elastic sensitive element can be divided into a sensing element and an elastic strain element. The receptor element converts the pressure into force to the most strain-sensitive part of the elastic strain element, while the strain gauge is attached to the maximum strain of the elastic strain element. In practice the more complex strain tube and strain beam types are of this type. The sensing elements are diaphragms, membrane boxes, bellows, borden tubes, etc. The elastic strain elements are cantilevered beams, fixed beams, Π-shaped beams, ring beams, thin-walled cylinders, etc. They can be combined into various types according to different needs. Strain gauge pressure sensors are mainly used to measure the dynamic or static pressure of flowing media, such as the pressure of inlet and outlet gases or liquids in power pipelines and equipment, the pressure of internal combustion engine pipelines, etc.

 

 

 

The principle and mechanism of strain gauge pressure sensors

 

1、The internal structure of metal resistance strain gauges

 

Resistance strain gauges consist of a base material, a metal strain wire or strain foil, an insulating protective sheet and a lead wire. Depending on the application, the resistance value of the strain gauge can be designed by the designer, but the range of resistance values should be noted: a resistance value that is too small will require too much driving current, while the heating of the strain gauge causes the temperature itself to be too high for use in different environments, making the resistance value of the strain gauge change too much, the output zero point drift is obvious and the zero adjustment circuit is too complex. The resistance is too large and the impedance is too high, making it less resistant to external electromagnetic interference. Generally, the resistance is a few tens to tens of kilo-ohms.

 

The above diagram shows the structure of a resistance strain gauge, which consists of a base material, a metal strain gauge or strain gage, an insulator and a lead wire. Depending on the use' the resistance of the resistance strain gauge can be designed designer' but the range of resistance values should be noted: the resistance value is too small' requiring too much driving current' while the strain gauge' gives off heat to make itself highly heated 'use in different environments' makes the strain gauge resistance vary too much 'output zero drift is noticeable' the zero adjustment circuit is too complex. However, the resistance is too high' the impedance is too high' and the resistance to external electromagnetic interference is poor. Generally a few tens of ohms to tens of kiloohms approximately.

 

2、The working principle of resistance strain gauge

 

The working principle of the metal resistance strain gauge is the phenomenon of change in the resistance value of the adsorption strain resistor' in the base material 'with mechanical deformation' named the resistance strain effect. The metal conductor resistance value can be indicated using the type '

 

where: lu - metal conductor resistivity (omega square centimetres per metre)

 

-Conductor cross-sectional area (cm2)

 

I conductor length (m)

 

We use the metal foil strain resistance as an example' when the buoyant exogenous process' its length and cross-sectional area can be changed' can easily be seen in the formula' its resistance value that can have changes' such as the exogenous process of the slender metal wire time' its length increases 'but the cross-sectional area decreases' the resistance value can increase. When a liquid compresses an exogenous process 'its length decreases while the increase in section' the resistance value decreases. As soon as the (usually investigative start and end of the resistance change in voltage) 'and thus the strain wire strain mood is determined

 

 

 

3、The working principle of resistance strain gauges

 

The working principle of metal resistance strain gauges is the phenomenon of strain resistance adsorbed on the base material to produce a change in resistance value with mechanical deformation, commonly known as the resistance-strain effect. The resistance value of a metal conductor can be expressed by the following formula

 

Where: ρ - the resistivity of the metal conductor (Ω-cm2/m)

 

S - the cross-sectional area of the conductor (cm2)

 

L - the length of the conductor (m)

 

When a metal wire is subjected to an external force, its length and cross-sectional area will change, as can be easily seen from the above formula, its resistance value will change, if the wire is stretched by an external force, its length will increase, while the cross-sectional area will decrease, the resistance value will increase. When the wire is compressed by an external force, the length decreases and the cross-sectional area increases, the resistance value decreases. The strain on the wire can be obtained by measuring the change in resistance (usually by measuring the voltage across the resistance).

 

 

 

    Changzhou Ruhrt Measurement & Control Systems Co., Ltd. provides you with an accurate, safe and reliable source of force measurement. We provide you with innovative, varied and stable products, offering the perfect solution for strain measurement.

Keyword:

Scan the QR code to read on your phone

Related Reading
 What are the materials of the force sensor?
2022.08.03
What are the materials of the force sensor?
   A force sensor consists of three parts: a bridging circuit made up of one or more elastomers (such as a Wheatstone bridge), elastomers that deform when subjected to stress, a resistance strain gauge that senses the deformation, an adhesive that holds the resistance strain gauge to the elastomer and conducts the strain, and a sealant that protects the electronic circuit. When the force sensor is subjected to an external force, the strain gauge attached to the elastomer will deform and cause a change in resistance. The change in resistance causes the Wheatstone bridge to lose balance and outputs an electrical signal that is linearly proportional to the external force. Next, let's introduce its materials: 1, elastomer material The elastomer material of the force sensor is usually made of metal, most of the available materials are aluminum alloy, alloy steel and stainless steel. The alloy material is not only rigid to ensure consistent deformation and deformation recovery, but also has good weather resistance and corrosion resistance. The main requirements of elastomers are to accurately transmit force information, maintain deformation consistency, and complete the reset under the same force. 2, strain gauge and resistance element materials The composition of the resistance strain gauge is complex and it is a composite manufacturing product. The combination of substrate and strain copper for strain gauges is constantly changing, with about 1,000 products available today. Generally, the substrate is a polymer film material, and the strain material is high purity constantan. The resistance grid lines with different induced deformation were optically treated and Constantan was etched on the substrate. Therefore, the quality of the resistance strain gauge is not only related to the metal purity of the matrix material and composite material, but also related to the composite process, etching process and technology, etching chemical materials and post-treatment process and material. 3, the material of the patch adhesive Two-component polymer epoxy series adhesives are mainly used for the installation of resistance strain gauges. The properties of polymer chemical products are closely related to physical and chemical indexes such as purity, molecular chain structure and size, storage time, component ratio, molecular modification, mixing method, mixing curing time, curing time, curing temperature, additives and percentage of each component. 4, sealant material Special silicone rubber sealant series are used in the initial phase of force sensors with insufficient welding processes and equipment. Silicone rubber has long-term chemical stability. Therefore, it has excellent anti-corrosion, moisture, aging resistance, insulation and other properties. It has long been the product of choice for all sealants. 5, load cell wire material The wire is still part of the force sensor. Personal experience of metal materials of force sensor wires with quality differences due to the use of household appliance wires. After all, the wire is the channel for bridge power supply, signal output and long line excitation voltage compensation. Silver-plated wire is definitely better than copper wire, and copper wire is definitely better than aluminum wire. Its role is self-evident. With the increase of various high frequency and radio wave interference, good shielding of force sensors is also an important method to protect signal stability. In addition, environmental corrosion, pest and mouse invasion, fire and flame retardant also require the sensor protective layer material to prevent corrosion, insect infestation, fire and explosion, and even need armor protection, shell protection and other methods.  
Read Article
What is a force sensor? What are the types?
2022.07.26
What is a force sensor? What are the types?
  Force is the direct cause of changes in material motion, and force sensors can detect mechanical quantities such as tension, tension, pressure, weight, torque, internal stress and strain. The force sensor is usually composed of a sensitive element and a conversion element, which is a device or equipment that can sense the specified measurement data and convert it into usable signals according to certain rules. Force sensors have been widely used in this new era, and are now widely used in the industrial field. In order to use the force sensor well, it is necessary to have a certain understanding of the definition and function of the force sensor. So, what is a force sensor? What are the types? Let's take a look! There are many kinds of force sensors, which can be divided into resistance strain sensors, piezomagnetic sensors and piezoelectric sensors according to different physical effects and detection principles. 1, strain type force sensor. Strain gauge force sensors are widely used in all force sensors. It has high measurement accuracy and can measure dynamic and static forces from small to large, and its usage accounts for about 90% of the total sensor. The working principle of the strain gauge force sensor is basically the same as that of the strain gauge pressure sensor, which is also composed of an elastic sensitive element and a strain gauge attached to it. The strain gauge force sensor first converts the measured force into the strain of the elastic element, and then reads the output by measuring the strain using the resistance strain effect. 2, voltage power sensor. When a ferromagnetic material is strained and pressed by an external force, its permeability will change with the magnitude and direction of the stress. When the tension acts, the permeability increases along the direction of the force, but decreases slightly in the direction of the vertical force, and the change of the permeability under pressure is just the opposite. This physical phenomenon is the piezomagnetic effect of ferromagnetic materials, which can be used for force measurement. 3. Piezoelectric sensor. Piezoelectric sensors can measure various dynamic forces, mechanical shock and vibration, and are widely used in the fields of acoustics, medicine, mechanics and navigation, with small size, light weight, high frequency response and high signal-to-noise ratio. According to the shape, the load cell can be divided into cantilever load cell, S-shaped load cell, plate load cell, box type load cell and spoke type load cell. Force sensors have penetrated into a wide range of fields, such as resource survey, ocean exploration, space development, industrial production, environmental protection, medical diagnosis, bioengineering, and even cultural relics protection. Force sensors have long penetrated into a wide range of fields, such as resource survey, ocean exploration, space development, industrial production, environmental protection, medical diagnosis, bioengineering, and even cultural relics protection. It is no exaggeration to say that almost every modern project, from the vast space, to the vast ocean, to a variety of complex engineering systems, can not be separated from a variety of force sensors.
Read Article
Analysis of characteristics and working principle of torque sensor
2022.01.11
Analysis of characteristics and working principle of torque sensor
    The emergence of the torque sensor itself should be used in all walks of life in a short time and become an indispensable variety in the sensor series. First, the characteristics of torque sensor: 1, can measure both static torque, can also measure rotary torque, can measure both static torque, can also measure dynamic torque. 2, high detection accuracy, good stability; Prevent interference; 3, small size, light weight, diverse installation structure, easy to install and use. Continuous measurement of positive and negative torques without repeating 0. 4, no conductive ring and other wear parts, can be high-speed long time running. 5, the sensor output high level frequency signal can be directly sent to the computer for processing. 6, measuring the strength of the elastomer can withstand high overload. Second, the torque sensor measurement principle: The special torsion strain gauge is attached to the measured elastic shaft as a strain glue to form a strain bridge and supply power to the strain bridge. The electrical signal of torsion of the elastic shaft can be measured. After amplifying this deformation signal, it undergoes pressure/frequency conversion and becomes a frequency signal proportional to the torsion reaction. The energy input and signal output of the system are handled by two sets of special annular transformers with a gap, thus providing contactless energy and signal transmission. Third, the torque sensor principle structure: The basic torque sensor-variable bridge is formed by attaching a special torsion measuring sheet to a special elastic shaft. Fixed on the shaft: (1) the secondary coil of the energy ring transformer, (2) the primary coil of the signal ring transformer, (3) the axis printed circuit, and the circuit board including the rectifier stable power supply, the instrument amplifier circuit, the V/F conversion circuit and the signal output circuit. 4. Working process of torque sensor: The sensor is supplied with a 15V power supply, a crystal oscillator on the magnetic circuit generates a 400Hz square wave, and an AC magnetoelectric power supply is generated through the TDA2030 power amplifier. The energy loop transformer T1 is transferred from the stationary primary coil to the rotating secondary coil. Results The AC power supply obtained 5V DC power supply through the rectifier filter circuit on the shaft. The power supply is used as a working power supply for the operational amplifier AD822. A high precision power supply consisting of a reference power supply AD589 and a dual operational discharge AD822 generates a 4.5V DC power supply. The power supply is used as a working power supply for bridging power supplies, amplifiers, and V/F converters. When the elastic shaft is twisted, the MV-class deformation signal detected on the deformation bridge is amplified by the instrument amplifier AD620 to a strong signal of 1.5v 1v, and then converted into a frequency signal by the V/F converter LM131. Through the signal ring transformer T2, it is possible to pass from the rotating primary coil to the stationary secondary coil, and then through the signal processing circuit filter of the sensor housing, shaping, obtaining a frequency signal proportional to the torque received by the elastic bearing, because the rotating transformer is in motion, zero between the static rings. With a gap of only a few millimeters, part of the sensor shaft is sealed inside the metal housing, forming an effective shield, and therefore has a strong anti-interference ability.
Read Article
What are the advantages and disadvantages of torque sensors?
2022.01.08
What are the advantages and disadvantages of torque sensors?
    The large-scale use of a thing has its advantages and disadvantages, such as torque sensors have advantages and disadvantages in the development process. Torque sensor, also known as torque sensor, torque sensor, torque sensor, torque meter, divided into dynamic and static two categories, of which dynamic torque sensor can also be called torque sensor, non-contact torque sensor. The following is a brief introduction to the advantages and disadvantages of torque sensors. First, the advantages of torque sensor With the continuous improvement and development of automatic control system, the reliability and response speed of torque sensor are put forward higher requirements. Torque sensors show the following trends. 1. The test system is developing in the direction of miniaturization, digitalization, intelligence, virtualization and networking. 2, from single function to multi-function development, including self-compensation, self-correction, adaptation, self-diagnosis, remote setting, state combination, information storage and memory; 3. Develop in the direction of miniaturization and integration. The detection part of the sensor can be miniaturized through rational design and optimization of the structure, and the IC part can integrate as many semiconductor components and resistors as possible into a single IC part, thus reducing the number of external parts. 4, static test to dynamic online detection direction; Second, the shortcomings of the torque sensor The success of the telemetry torque meter lies in overcoming two defects of the electric slip ring. But there are three drawbacks. One is vulnerable to the use of field electromagnetic waves. The second is because it is a battery power supply, so it can only be used in the short term. Third, the structure is attached to the rotating axis, which is easy to cause the dynamic balance problem of high speed, so it is more prominent on the small distance and small diameter axis. The digital torque sensor absorbs the advantages of the above methods and overcomes the defects. Based on the deformation sensor, two sets of rotary transformers are designed to realize the non-contact transmission of energy and signal. The transmission of the torque signal has nothing to do with rotation or not, nothing to do with the speed, and nothing to do with the direction of rotation. Three, the main characteristics of the torque sensor are as follows: Dynamic and static torque can be measured. The stability of the check is very good, the anti-interference performance is very strong, and the accuracy is very good. It does not need to adjust 0 each time when measuring, and can continuously measure the positive and negative torque. Its signal output can be manipulated by you, with a choice of pulse wave or waveform - square wave. Wide measuring range. There are 0 to 1000Nm standards to choose from, and some non-standard ones such as 20,00 NM, 100,000 NM, 100,000 NM, etc., can be customized using a special range of customization. The volume is very small, the heavy sensor can be used independently from the secondary instrument, and only the 15V and -15V power supply provided by the socket pin number can output the pulse wave or equal square wave frequency signal proportional to the impedance and the forward relationship, which is very light and convenient to install.
Read Article

Follow us for more information

  • 官方微信 【 Official WeChat 】
  • 手机网站 【 Mobile Website 】
Username used for comment:
Feedback
Description:
We use cookies to improve our site and your shopping experience. By continuing to browse our site you accept our cookie policy. Find out more
Cookie
Copyright © 2021 Changzhou Right Measurement and Control System Co., Ltd
www.300.cn