What are Pressure Sensors?

A pressure sensor (Pressure Transducer) is a device or device that can sense the pressure signal and can convert the pressure signal into a usable output electrical signal according to a certain rule.

Pressure Sensor

A pressure sensor (Pressure Transducer) is a device or device that can sense the pressure signal and can convert the pressure signal into a usable output electrical signal according to a certain rule.

A pressure sensor usually consists of a pressure-sensitive element and a signal processing unit. According to different test pressure types, pressure sensors can be divided into gauge pressure sensors, differential pressure sensors and absolute pressure sensors.

-Extracted from JJG860-2015

Pressure sensor is the most commonly used sensor in industrial practice, and it is widely used in various industrial self-control environments, involving water conservancy and hydropower, railway transportation, intelligent buildings, production self-control, aerospace, military, petrochemical,

Heavy-duty pressure sensors are one type of sensor, but we rarely hear about this type of pressure sensor. It is commonly used in transportation applications by monitoring pneumatic, light-load hydraulic pressure, brake pressure, oil pressure, transmission, and The pressure, hydraulic force, flow rate and liquid level of key systems such as truck / trailer air brakes to maintain the performance of heavy-duty equipment.
The heavy load pressure sensor is a pressure measuring device with a housing, a metal pressure interface and a high-level signal output. Many sensors are equipped with a circular metal or plastic housing, which is cylindrical in shape, with a pressure interface at one end and a cable or cable at the other end.

The basic principle of multi-sensor information fusion technology is like the process of the human brain's comprehensive processing of information. Various sensors perform multi-level and multi-space information complementation and optimized combination processing, and finally produce a consistent interpretation of the observation environment. In this process, we should make full use of multi-source data for reasonable control and use, and the ultimate goal of information fusion is to derive more useful information through multi-level and multi-faceted combination of information based on the separated observation information obtained by each sensor. This is not only to take advantage of the cooperative operation of multiple sensors, but also to comprehensively process data from other information sources to improve the intelligence of the entire sensor system. ^[1]

1.piezoresistive pressure sensor

The resistance strain gauge is one of the main components of a piezoresistive strain sensor. The working principle of metal resistance strain gauges is the phenomenon that the resistance of the strain resistance absorbed on the base material changes with the mechanical deformation, which is commonly known as the resistance strain effect.

2.Ceramic pressure sensor

The ceramic pressure sensor is based on the piezoresistive effect. 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. The piezoresistive effect makes the bridge generate 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 / 3.3mV / V according to the different pressure ranges. Strain sensors are compatible.

3. Diffused silicon pressure sensor:

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

4. Sapphire pressure sensor:

Utilizing the strain-resistance principle and using silicon-sapphire as the semiconductor sensitive element, it has unparalleled metrological characteristics. Therefore, semiconductor-sensitive components made of silicon-sapphire are insensitive to temperature changes and have very good operating characteristics even at high temperatures; sapphire's radiation resistance is extremely strong; in addition, silicon-sapphire semiconductor-sensitive components, no pn drift.

5. Piezoelectric pressure sensor:

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

When selecting a pressure sensor, we must consider its comprehensive accuracy, and which aspects of the accuracy of the pressure sensor are affected? In fact, there are many factors that cause sensor errors. Let s pay attention to the four inevitable errors. Initial error.

First offset error: due to

Install correctly

Usually the damage of the high temperature melt pressure sensor is caused by its improper installation position. If the sensor is forcibly installed in too small a hole or the shape is irregular

Pressure is one of the important parameters in industrial production. In order to ensure the normal operation of the production, the pressure must be monitored and controlled. The following are common terms used in the selection of pressure sensors:

Standard pressure

The pressure expressed by atmospheric pressure is greater than atmospheric pressure is called positive pressure; less than atmospheric pressure is called negative pressure.

Absolute pressure

The magnitude of pressure expressed in terms of absolute vacuum.

Relative pressure

The amount of pressure for the comparison object (standard pressure).

Atmospheric pressure

Refers to atmospheric pressure. Standard atmospheric pressure (1atm) corresponds to the pressure of a mercury column at a height of 760mm.

vacuum

Refers to a pressure state below atmospheric pressure. 1Torr = 1/760 barometric pressure (atm).

Detection pressure range

Refers to the pressure range of the sensor.

Can withstand pressure

When the pressure is restored, the performance can withstand pressure without degradation.

Round trip accuracy

At a certain temperature (23 ° C), when the pressure is increased or decreased, the full-scale value of the detected pressure is used to remove the pressure value at the operating point, which is obtained by removing the pressure value that is inverted.

Accuracy

At a certain temperature (23 ° C), when zero pressure and rated pressure are applied, the value obtained by subtracting the value deviating from the specified value of the output current (4mA, 20mA) with the full scale value. The unit is expressed as% FS.

Linear

The analog output changes linearly to the detection pressure, but has deviations from the ideal straight line. Linearity is the value that expresses this deviation as a percentage of the full scale value.

Hysteresis (linear)

Use zero voltage and rated voltage to draw an ideal straight line between the output current (or voltage) value, take the difference between the current (or voltage) value and the ideal current (or voltage) value as the error, and then find the pressure rise and fall Time error value. The value obtained by dividing the maximum value of the absolute value of the difference by the full-scale current (or voltage) value is the hysteresis. The unit is expressed as% FS.

Lag

The value obtained by dividing the difference between the output ON-point pressure and the OFF-point pressure by the full-scale value of the pressure is the hysteresis.

Non-corrosive gas

Refers to substances (nitrogen, carbon dioxide, etc.) and inert gases (argon, neon, etc.) contained in the air.

Pressure sensors are mainly used in the fields of booster cylinders, boosters, gas-liquid booster cylinders, gas-liquid boosters, presses, compressors, and air-conditioning refrigeration equipment.

1.Application in hydraulic system

The pressure sensor in the hydraulic system is mainly used to complete the closed-loop control of force. When the control spool is suddenly moved, a peak pressure that is several times the system operating pressure is formed in a very short time. In typical mobile machinery and industrial hydraulics, if such extreme conditions are not considered in the design, any pressure sensor will be quickly destroyed. Need to use an impact-resistant pressure sensor. There are two main methods for pressure sensors to achieve impact resistance. One is to change the strain gauge chip, and the other is an external coil. The first method is generally used in hydraulic systems, mainly because Easy to install. Another reason is that the pressure sensor is also subject to uninterrupted pressure pulsations from the hydraulic pump.

2. Application in safety control systems

Pressure sensors are often used in safety control systems. The main target area is the air compressor's own safety management system. 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.
Applications in the field of safety control generally consider performance, cost considerations, and practical convenience and safety. It has proven to be very effective in selecting pressure sensors. The pressure sensor uses processing technology of mechanical equipment to mount some components and devices such as signal conditioners on a small chip. Therefore, its small size is one of its advantages. In addition, its low price is another of its advantages. To a certain extent, it can improve the accuracy of system testing. In the safety control system, the pressure brought by the compressor is controlled to a certain extent by installing a pressure sensor in the pipeline equipment of the air outlet. This is a certain protection measure and a very effective control system. When the compressor starts 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. Application in injection mold

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

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

5.Used to promote sleep

The pressure sensor itself cannot promote sleep. We just place the pressure sensor under the mattress. Due to the high sensitivity of the pressure sensor, when a person performs movements such as turning over, heartbeat, and breathing, the sensor analyzes this series of information to infer sleep What is the state of a person's sleep, and then analyze the sensor, collect the sensor signals to get sleep data such as heartbeat and breathing rhythm, and finally process all the data into a single track, of course, it can compress your night's sleep into a The first few minutes of music.

6.Applied to compressors, air-conditioning cooling equipment

Pressure sensors are often used in air presses, as well as air-conditioning and refrigeration equipment. These sensors are small in size and easy to install. The pressure port is generally designed with a dedicated valve pin.

There are many types of pressure sensors, and their performances are also quite different. How to choose more suitable sensors for economical and reasonable use.

Rated pressure range

The rated pressure range is a pressure range that meets the standard specified values. That is, between the highest and lowest temperature, the sensor output meets the pressure range of the specified operating characteristics. In actual application, the pressure measured by the sensor is within this range.

2. Maximum pressure range

The maximum pressure range refers to the maximum pressure that the sensor can withstand for a long time without causing permanent changes in the output characteristics. In particular, semiconductor pressure sensors generally reduce the rated pressure range significantly in order to improve linearity and temperature characteristics. Therefore, it will not be damaged even after continuous use above the rated pressure. Generally the maximum pressure is 2-3 times the highest value of the rated pressure.

Damage pressure

Damage pressure is the maximum pressure that can be applied to the sensor without damaging the sensor element or sensor housing.

Linearity

Linearity refers to the maximum deviation of the linear relationship between the sensor output and pressure in the working pressure range.

5. Pressure Hysteresis

It is the difference between the sensor output when the minimum working pressure and the maximum working pressure approach a certain pressure at room temperature and within the working pressure range.

6. Temperature range

The temperature range of the pressure sensor is divided into a compensation temperature range and an operating temperature range. The compensated temperature range is the temperature range in which the accuracy enters the rated range due to the application of temperature compensation. The working temperature range is the temperature range to ensure the normal operation of the pressure sensor.

Technical parameters (range 15MPa-200MPa)

Parameter Unit Technical Index Parameter Unit Technical Index

Sensitivity mV / V 1.0 ± 0.05 Sensitivity temperature coefficient % F · S / 10 ± 0.03

Non-linearity % F · S ± 0.02 ± 0.03 Working temperature range -20 + 80

Hysteresis% F · S ± 0.02 ± 0.03 Input resistance 400 ± 10

Repeatability % F · S ± 0.02 ± 0.03 Output resistance 350 ± 5

Creep% F · S / 30min ± 0.02 Safety overload% F · S 150% F · S

Zero output % F · S ± 2 Insulation resistance M 5000M (50VDC)

Zero temperature coefficient % F · S / 10 ± 0.03 Recommended excitation voltage V 10V-15V

Pressure sensors are used in various industries, especially in the industry. Pressure sensors are generally required in the industry to prevent corrosion. The pressure sensor joints and cavities are imported and processed in stainless steel as the body of the pressure transmitter. The stainless steel material has high corrosion resistance and good attenuation performance, and can monitor any medium compatible with 316L. Below we also introduce the anti-corrosion skills of pressure sensors.
First, find out if the tested medium is compatible with 316L: 316, 317L alloys did not show corrosion during 100 hours of 5% salt spray testing. Secondly, when purchasing sensor products, consult the supplier whether the medium has an impact on the pressure sensor; through the selection of the anti-corrosive material of the bomb body, in order to meet the needs of users. Finally, we can adopt the isolation method: Molybdenum 2 titanium and tantalum sheets are in front of the pressure transmitter, and the pressure between the diaphragm and the ballistic tube is transmitted by methyl silicone oil. The minimum range can be 0 ~ 100kPa. Corrosion resistance, you can add a layer of F46 diaphragm, but the sensitivity of the instrument is reduced. F46 can also be used directly as the isolation diaphragm. Fluorine oil can be used as the transfer fluid, which can double-isolate.
When the pressure sensor is found to be incompatible with the medium, it must be replaced immediately. For some special media, we can use special materials or special structures for measurement. The pressure sensor will definitely be more widely used in the future, so As a manufacturer, we must actively develop new pressure sensors to meet the needs.

1. Technological advancements in major verticals, including oil and gas, automotive and healthcare, have led to the evolution of multiple applications and pressure sensor capabilities.

2. The automotive sector is one of the most important users of pressure sensors. The surge in automotive production has led to an increasing demand for pressure sensors and related components.

3. Motor vehicle safety has become an important aspect of the entire automotive industry. Strict government regulations surrounding this feature will help promote the demand for pressure sensors in the automotive industry.

4. Micro-Electro-Mechanical Systems (MEMS) and Nano-Electro-Mechanical Systems (NEMS) -based technologies have been widely welcomed by the public, and their adoption has increased dramatically, leading to the growth of the pressure sensor market.

5. The consumption of consumer electronics pressure sensors has increased significantly, and has become the fastest growing application field in the entire market.

6. The maturity of end-use industries such as the automotive and healthcare markets has become a major challenge hindering North American and European pressure sensor markets.

7. The rapid industrialization and automotive production in Asian countries such as China, Japan, India and South Korea can be attributed to the development of the Asia Pacific pressure sensor market.

8. The development of smart city infrastructure in Asia Pacific and the Middle East holds great potential for future growth.

9. Consumers worry about rising costs of installing and replacing pressure sensors, which could affect pressure

Modern sensors vary widely in principle and structure. How to select sensors reasonably according to the specific measurement purpose, measurement object and measurement environment

When selecting a pressure sensor, you need to pay attention to many issues, such as the range, accuracy of the pressure sensor, the temperature characteristics of the pressure sensor, and the chemical characteristics of the pressure sensor to be considered.
For example, sensors are used to measure gas pressure and liquid pressure. Gas is a compressible fluid. When it is increased, it will store a certain amount of compression energy, and when it is decompressed, it will be released with kinetic energy to apply a shock wave to the elastic film of the sensor. The pressure sensor is required to have a large overload capacity. Liquid is an incompressible fluid. When the pressure sensor is installed, tightening the bolt without compressible space can increase the liquid pressure beyond the pressure limit of the elastic membrane, causing the elastic membrane to rupture. Since this happens again and again, the pressure sensor is required to have a large overpressure capability. When the working environment of the pressure sensor is harsh, for example, there are large vibrations, shocks, and large electromagnetic interference, which places stricter requirements on the sensor. Not only is the overpressure capability strong, but also the mechanical seal is reliable, anti-loosening, and the sensor is installed correctly. The sensor's own leads, pins and external wires should be electromagnetically shielded, and the shield should be well grounded. In addition, the compatibility of the pressure sensor with the fluid medium being measured should be considered. For example, the elastic membrane structure of the sensor should be separated from the corrosive medium. At this time, a stainless steel corrugated sleeve sensor is used, and the sensor uses silicon oil as the pressure transmitting medium. When the sensor detects the pressure of flammable and explosive media, a small excitation current is used to prevent sparks and sparks when the elastic membrane is broken, and increase the pressure resistance of the pressure sensor jacket.
Only by understanding the operating method of the pressure sensor can a better selection of the pressure sensor, especially the pressure sensor is developing rapidly, so it is very necessary to understand the operating method of the pressure sensor.

We often use pressure sensors. We must pay attention to protecting the pressure sensor during use, because the pressure sensor is protected by stainless steel, but the pressure sensor is still easy to damage, especially the improper use can easily cause damage to the pressure sensor and cause loss.

First of all, the sensor must be used out of range. Do not apply pressure exceeding the rated pressure. If a pressure higher than the withstand pressure is applied, it may cause damage. The second is the use environment, avoid using in flammable and explosive gas environments. There is also a short circuit between the power supply voltage and the load. When using it, do not exceed the operating voltage range. If a voltage greater than the operating voltage range is applied, it may cause cracking or burnout. Avoid shorting the load. Failure to do so may cause cracking or burning. Another thing that is relatively rare is incorrect wiring, to avoid incorrect wiring of power supply polarity. Failure to do so may cause cracking or burning.

The pressure sensor must learn how to protect it when it is used, otherwise it will be easily damaged and cause production loss. Of course, as long as we operate correctly according to the manufacturer's instructions to avoid the above problems, the pressure sensor can still work for a long time. . Some pressure sensors can be used for years or even decades. The main thing is to learn how to protect it.

The main piezoelectric materials used in piezoelectric sensors include quartz,

First of all, it is necessary to prevent the transmitter from contacting the corrosive and overheated medium to avoid damaging it; the pressure tube should be installed in a place with small temperature fluctuations; when measuring some media with high temperature The condenser must be connected at this time. This is because the temperature of the transmitter must be prevented from exceeding a certain limit when it is working; it must be kept in a clear conduit; when it is used in cold winter, if the transmitter is installed outdoors If you do, you must also take good anti-freezing measures. This is to prevent the liquid in the pressure port from expanding due to freezing, which easily damages the sensor. When the user connects the cable, the cable must be worn. Waterproof joints or coiled tubing and then tighten the sealing nut, this can prevent liquid and other things from leaking into the transmitter housing through the cable. Now let's talk about the precautions when measuring liquid pressure and gas pressure, everyone should distinguish clearly. When measuring the liquid pressure, the pressure taking port must be opened at the side of the process pipeline. This is to prevent slag precipitation. At this time, the place where the transmitter is installed should be protected from the impact of other liquids.

Pressure sensors are one of the most commonly used sensors in industrial practice. The output of a common pressure sensor is generally an analog signal. An analog signal refers to a continuous signal with information parameters within a given range. Or, in a continuous time interval, the characteristic quantity representing the information can be presented as a signal of any value at any instant. The pressure sensor we usually use is mainly manufactured by using the piezoelectric effect. Such a sensor is also called a piezoelectric sensor.

Generally, when selecting, you need to have the following common sense:

1. Brand Misunderstanding: Many people think that domestic products are not easy to use, and even they cannot be used.

2. Misunderstanding of accuracy: When choosing products, everyone always thinks that accuracy is the most important. In fact, from a certain perspective: stability is more important than the accuracy of the product. The accuracy selection should be based on high stability .

3, the pursuit of cheap: quality and cheap this is what everyone wants to see; but in fact, high-quality products determine its price will be relatively high.

4. Select the appropriate range, appropriate accuracy, suitable installation method, and appropriate output method.

When using it, you should also understand the following common sense:

1. Check the size of the mounting holes and keep the mounting holes clean;

2. Correct installation and selection of appropriate locations;

3. Carefully clean and keep dry;

4. Avoid high and low temperature interference, high and low frequency interference, and electrostatic interference;

5. Prevent pressure overload;

Pressure sensor is the most commonly used sensor in China's industrial practice. It is widely used in various industrial self-control environments, involving water conservancy and hydropower, railway transportation, intelligent buildings, production self-control, aerospace, military, petrochemical, oil wells, electricity, Ships, machine tools, pipelines and many other industries, so it is necessary to have a comprehensive understanding of them.