What is a gas pressure sensor?
Gas Pressure Sensors are also called Gas Pressure Transducers. Gas Pressure Sensors convert gas pressure into standard electrical signals, such as 4~20mADC. Measurement, indication and process adjustment are carried out by supplying secondary instruments such as indicating and alarming instruments, recorders, and regulators.
Gas pressure measurement is widely used in the field of industrial process control for process control and monitoring. Different gases have different properties, so different pressure sensors and transmitters are required to measure different gas pressures. For example, measuring oxygen, hydrogen, chlorine, compressed air, high temperature gas, etc.
gas pressure measurement
Gas pressure sensors are designed (or configurable) to measure gas pressure in different ways. In industrial settings, they can be used to measure the velocity of gas flow (sometimes called “shock pressure”), confirm the presence of suction, manage source pressure, or test for leaks.
(1). Gauge pressure is measured relative to ambient atmospheric pressure. Atmospheric pressure at sea level is about 100kPa (14.7 PSI). Sensors built into tire air pumps measure pressure this way, showing the air pressure inside the tire relative to the local atmospheric pressure. A reading of zero indicates equal internal and external pressure.
(2). Sealed air pressure sensors are similar to gauge air pressure sensors. But are pre-calibrated to measure air pressure relative to sea level atmospheric pressure. Therefore, if the device is taken to a different altitude or location, its readings will not change. More about: Diaphragm pressure gauge working principle.
(3). Vacuum pressure is a measure of the negative difference between the gas pressure at a given location and the atmospheric pressure.
(4). Absolute air pressure is measured from zero or perfect vacuum (0 PSI). Again, unlike gauge pressure, this is not affected by the conditions surrounding the device. These conditions will vary with altitude and other factors.
(5). Differential pressure is the difference between two gas pressures. For example, the pressure difference in two gas hoses connected to the sensor. As with gauge pressure, a sensor may be able to measure changes in air pressure in either direction (i.e. positive or negative).
In addition to different types of measurements, some barometric pressure sensors are also designed to measure rapid pressure changes in dynamic environments. For example combustion pressure in engine cylinders or gas turbines.
Extended Reading: 4-20ma pressure transducer wiring diagram
Oxygen (O2) Pressure Measurement
Oxygen plays an important role in the smelting process, chemical industry, national defense industry, and medical care. However, the production and use of oxygen is extremely prone to combustion and explosion.
According to the mechanism of combustion and explosion “three elements” (combustibles, oxidants, excitation energy). The stronger, the more dangerous. Potential excitation energy sources for combustion or explosion are generally in the following ways: friction, compression heat, impact force, electric arc, resonance, etc.
For oxygen pressure measurement, a clean pressure sensor and a transmitter filled with inert oil is a safer choice. The risk of financial and time loss due to maintenance or faulty replacement is greatly reduced.
During the construction of industrial oxygen pipelines, multi-channel cleaning processes such as rust removal, scrubbing, sandblasting, blowing, degreasing, pickling, etc. should be carried out to remove oil and impurities in the pipelines so that they can meet the conditions for transporting oxygen media. And in accordance with relevant standards Check and accept. It can be used only after passing the test.
Extended reading: High accuracy pressure transducers
Featured Oxygen Sensors and Transducers
For oxygen pressure measurement, choosing a clean instrument filled with inert oil not only improves the safety level, but also greatly reduces the risk of economic and time loss caused by maintenance or failure replacement.
The pressure sensor for oxygen measurement supplied by Sino-Inst is required for the application of oxygen pressure measurement. The sensor product is filled with Fluorolube® oil. At the same time, oil-free technology is used for production. Finally, the sensor and transmitter are cleaned and packaged according to the oxygen level cleaning process.
The above sensors can be used in hazardous locations, including explosion-proof, intrinsically safe products. And it can be used in the occasions involving oxygen pressure measurement such as factories and hospitals.
The special pressure sensor for oxygen measurement must be cleaned strictly by oxygen grade cleaning process. Ensure that the sensor is clean and free of oil, corrosion, scaling, particles and other impurities. During the oxygen pressure measurement process, the potential risk of oxygen combustion or explosion caused by sensor oil pollution is completely solved.
Oxygen grade cleaning operations must be carried out in a dust-free and clean environment. To be operated by trained and qualified professionals. Use a special cleaning agent to clean the sensor and its accessories. Cleaning needs to go through multiple processes such as soaking, wiping, scrubbing, rinsing, drying, and sealing packaging. At the same time, during the cleaning process, special inspection equipment and precision instruments are used to conduct qualitative and quantitative inspections of the oil on the surface of the sensor. Make sure the sensor is clean.
Sino-Inst has an oxygen level cleaning platform, perfect cleaning process and quality control process. It cleans and seals the pressure sensor and pressure transmitter for measuring oxygen and high cleanliness.
Extended Reading: strain gauge pressure transducer
Hydrogen (H2) Pressure Measurement
Hydrogen (H2) is an extremely flammable, colorless, and odorless gas at normal temperature and pressure. Hydrogen has strong reducing properties and is a common industrial gas. It has a large number of applications in chemical, electronic, automotive, aerospace and other industries.
Hydrogen is easy to diffuse rapidly. When the ratio of hydrogen mixed with air exceeds 4%, it will become a combustible gas. Therefore, strict process and process control are required in the process of production, storage and transportation.
Since the hydrogen atom is very small, it will diffuse through the lattice of the diaphragm (usually stainless steel), thereby penetrating into the cavity filled with silicone oil. After long-term use, the infiltrated gas can damage the sensor.
Although gold is less permeable than stainless steel, gold-plated diaphragms are an effective way to prevent hydrogen permeation.
Extended Reading: Smart pressure transmitter working principle
Featured Hydrogen Pressure Sensors and Transducers
The pressure sensor dedicated to hydrogen measurement has many advantages in the pressure monitoring application of hydrogen production and purification equipment, hydrogen storage and transportation equipment.
In the process of measuring hydrogen pressure with a piezoresistive isolated pressure sensor. Since the atoms of hydrogen are very small, they will diffuse through the lattice of the diaphragm (usually stainless steel), thereby penetrating into the cavity of the sensor filled with silicone oil. Over time, the permeated gas can seriously affect the performance of the sensor. Effectively prevent the occurrence of “hydrogen embrittlement” and “hydrogen permeation”.
- Measuring range: -100kPa…0kPa~35kPa…20MPa
- Isolated structure, suitable for the measurement of hydrogen medium;
- Pure flat membrane structure, using no dead angle full welding technology, the minimum thickness of gold plating layer is greater than 2μm;
- The purity of gold plating on the surface reaches 99.8%;
The problem of hydrogen storage and transportation is an important factor affecting the cost of hydrogen. Pipeline hydrogen transportation has low cost and low energy consumption. It can realize continuous, large-scale and long-distance transportation of hydrogen energy. It is an important breakthrough direction for hydrogen storage and transportation problems.
It can be applied to hydrogen transportation scenarios such as hydrogen transportation vehicles. At the same time, it is also very suitable for pressure measurement of hydrogen storage cylinders and tank trucks and other gas and liquid hydrogen in hydrogen transportation.
Read more about: Types of biogas flow meters
Chlorine (CL2) Pressure Measurement
Chlorine is a simple substance formed by chlorine, with the chemical formula Cl2. It is yellow-green under normal temperature and pressure. It is a highly toxic gas with a strong pungent smell. It is suffocating and has a higher density than air.
Melting point -101.00°C, boiling point -34°C. Soluble in water and alkali solution, easily soluble in organic solvents (such as carbon tetrachloride), hardly soluble in saturated saline. It is easy to compress and can be liquefied into yellow-green oily liquid chlorine.
Generally, steel, iron, copper, nickel, etc. are resistant to dry chlorine, but once chlorine gas is mixed with a small amount of water, it will generate hypochlorous acid and hydrochloric acid, which are highly corrosive to most metals.
Therefore, pressure sensors and transmitters used for chlorine pressure measurement must use special corrosion-resistant housing and diaphragm materials to ensure reliable and accurate measurement.
More about: The Difference Between Absolute And Gauge Pressure
Featured Chlorine Pressure Sensors and Transducers
There are 2 types of chlorine pressure transmitters that are common:
- Dry chlorine. Pure chlorine gas is non-corrosive. It can be said that it is economical and affordable to use ordinary pressure gauges to measure pressure.
- Moist chlorine. If chlorine contains water, chlorine and water will react chemically to synthesize HCL and chloride ions. We all know that chloride ions are highly corrosive, and a special pressure transmitter must be used to measure pressure in order to resist the corrosion of chloride ions.
The pressure gauge used to measure chlorine gas containing moisture is a dedicated diaphragm pressure transmitter. The material of the instrument diaphragm isolator is 316L+F4, and the isolation diaphragm is 316L+F4. This diaphragm pressure transmitter is the most cost-effective. Isolation diaphragm can also choose Ta+F4. The price of this chlorine pressure transmitter is relatively high.
According to the actual situation of the user, select the chlorine gas pressure transmitter suitable for the actual situation on site.
Extended Reading: MEMS Pressure Sensors
High Temperature Gas Pressure Sensors
High Temperature Gas Pressure Sensor for pressure measurement of high temperature gas. High temperature up to 800 ℃.
High Temperature Pressure Sensor with high temperature resistant pressure core or sapphire core as pressure measurement material. After high reliability amplifier circuit and precise temperature compensation. The absolute or gauge pressure of the measured medium is converted into standard electrical signals such as 4 ~ 20mA, 0 ~ 5VDC, 0 ~ 10VDC. It is also widely used in industry. Collect pressure signals at the points of some high-temperature steam and fluid pipes.
- Range: -100KPa ~ 0 ~ 100MPa optional
- Accuracy: ± 0.5% FS (composite error including non-linear repeatability hysteresis)
- Output signal: 4 ~ 20mADC (two-wire system), 0 ~ 10mADC, 0 ~ 20mADC, 0.5 ~ 4.5VDC, 0 ~ 5VDC, 1 ~ 5VDC, 0 ~ 10VDC (three wire system)
- Power supply voltage: 5 ~ 40VDC (two-wire system), 15 ~ 40VDC (three-wire system)
- Medium temperature: -40 ℃ ~ 200 ℃ -40 ℃ ~ 400 ℃ -40 ℃ ~ 600 ℃ -40 ℃ ~ 800 ℃
- Ambient temperature: -30 ℃ ~ 105 ℃
- Pressure connection: M20 * 1.5 M22 * 1.5 M16 * 1.5 M11 * 1 NPT1 / 4 NTP1 / 2 NTP3 / 8 G1 / 8 G1 / 2 G1 / 4 G3 / 8,1 / 2-20UNF, etc. Other threads can be according to customer requirements design
Frequently asked questions
There are many types of pressure sensors. The following are some commonly used pressure sensors.
Ceramic piezoresistive pressure sensor: with high precision and high stability of measurement. The electrical insulation degree is greater than 2KV, the output signal is strong, and the long-term stability is good. There is no choice between micro range and large range, it is only applicable to gauge pressure measurement.
Single crystal silicon pressure sensor: wide measuring range, high precision. Wide operating temperature, good stability, excellent static pressure characteristics. It has good one-way compression characteristics.
Capacitive pressure sensor: low input force and component Ru energy. High dynamic response, small natural effects. Good environmental adaptability.
Sapphire pressure sensor: The main advantage is that it can measure high-temperature media and is not sensitive to temperature changes. The drift in time at high temperature is the lowest among these types of sensors. Sapphire can be the most
The large range is up to 160MPa, while the maximum range of diffused silicon is 35MPa.
Quartz crystal pressure sensor: high frequency response pressure sensor, quick response. The digital output is stable and reliable, with strong anti-interference. Suitable for long-distance transmission, eliminating the analog
The complexities of digital conversion and the errors it creates.
Sputtering thin film differential pressure sensor: the outstanding feature is that it is less affected by temperature. When the temperature changes by 100°C, the zero point drift is only 0.5%. Its temperature performance is much better than that of diffused silicon, and it can
Features such as use under harsh environmental conditions.
Strain-type differential pressure sensor: The most widely used is the strain-type pressure sensor. It has extremely low price and high precision and good linear characteristics.
There are two types of resistance strain gauges: metal and semiconductor. Metal strain gauges are divided into wire type, box type, and film type. Semiconductor strain gauges have the advantages of high sensitivity and small lateral effects.
The above pressure sensors are commonly used by us. Each has its own characteristics, and the type is determined according to the needs when choosing.
Read more: Pressure Sensor Applications-Featured Industry Applications
For example, Below is a pressure sensor for measuring high temperature gas.
The parameters are roughly:
- Pressure range: 0-30psig,
- 300 degrees Celsius high temperature
- without local display;
- 4-20mA signal output;
- Mounting thread 7/16″-20UN-2A (Male SAE-4);
The above parameters are customized according to user requirements. Even the body length of the sensor is customized to the 160mm length requested by our customer.
Read More: What Is A Pressure Sensor Example?
A pressure sensor is a device or device that can sense pressure and convert the pressure signal into an electrical signal output according to certain rules.
Pressure sensors usually refer to component-level products with non-standard mV signal output. They are the core components of pressure transmitters.
Pressure transmitters measure the liquid level, density and pressure of liquids, gases or vapors, acting on sensitive diaphragms. In general, a pressure transmitter is mainly composed of three parts: a load cell sensor (also called a pressure sensor), a measurement circuit, and a process connection.
It can convert physical pressure parameters such as gas and liquid felt by the load cell sensor into a standard electrical signal (such as 4~20mADC, etc.). It can be used to supply secondary instruments such as indicating alarms, recorders, and regulators for measurement and indication. and process regulation.
The installation position of the pressure transmitter on the process pipeline is related to the measured medium. The following conditions should be considered during installation:
- Try to avoid direct contact between the transmitter and the corrosive or overheated measured medium.
- To prevent dross from depositing in the pressure guiding tube.
- The pressure guiding tube should be as short as possible.
- The liquid column pressure in the pressure guiding tubes on both sides should be kept balanced.
- The pressure guiding pipe should be installed in a place with small temperature gradient and temperature fluctuation.
When measuring liquid flow, the pressure tap should be opened on the side of the process pipeline to avoid sedimentation of dross. At the same time, the transmitter should be installed next to or below the pressure port so that the air bubbles can be discharged into the process pipeline.
When measuring gas flow, the pressure tap should be opened on the top or side of the process pipeline. And the transmitter should be installed next to or above the process pipeline so that the accumulated liquid can easily flow into the process pipeline.
When using a transmitter with a side relief valve in the pressure chamber, the pressure tap should be opened on the side of the process pipe. For example, when the measured medium is liquid, the relief valve of the pressure transmitter should be installed on it so as to exclude the gas infiltrated in the measured medium. When the measured medium is gas, the discharge valve of the transmitter should be installed below to discharge the accumulated liquid. The pressure chamber can be turned 180° so that the relief valve above it can be changed to the bottom.
The transmitter can be installed directly at the measuring point. It can be installed on the wall, or clamped on the pipeline with the installation plate (transmitter accessory).
Hydrogen embrittlement usually manifests as delayed fracture under stress. The phenomenon of delayed fracture occurs because the hydrogen in the part diffuses to the stress concentration part and gathers the metal defects in the stress concentration part (atomic lattice dislocation, holes, etc.).
Hydrogen diffuses into these defects, and hydrogen atoms change into hydrogen molecules to generate enormous pressure. This pressure and the residual stress inside the material and the external stress of the material form a resultant force. When this resultant force exceeds the yield strength of the material, fracture occurs.
Since hydrogen embrittlement is related to the diffusion of hydrogen atoms. Diffusion takes time, and the speed of diffusion is related to concentration gradient, temperature and material type.
A pressure transmitter is a device that converts pressure signals into electrical signals for control and remote transmission. Its core components are single crystal silicon resonant sensors and measuring capsules.
In order to reduce the pressure loss in the transmission process and prevent corrosion by the measurement medium. Generally, the metal thin-walled material with certain elasticity and anti-corrosion performance (the thickness is between 40 ~ 80um, which is slightly different for each equipment supplier) is selected to make the measuring diaphragm. Common measuring diaphragm materials include 316L stainless steel, Hastelloy, tantalum, titanium and many other types.
Since the thickness of the measuring diaphragm is less than 0.1mm, conventional pressure transmitters are prone to hydrogen embrittlement and are affected under harsh working conditions (high temperature and high pressure and high concentration of hydrogen). As a result, the toughness of the measuring diaphragm degrades and loses its elasticity, and cavity bulges or cracks appear.
Over time the hydrogen molecules can even penetrate the measuring diaphragm into the insulating silicone fluid. The presence of air bubbles increases losses during pressure transmission. It will also directly interfere with the measurement effect of the pressure transmitter, resulting in zero drift of the pressure transmitter and unstable output. Measurement errors and fluctuations in pressure measurement parameters occur. In more serious cases, the pressure transmitter may even be damaged, resulting in a safety accident.
Therefore, the selection of the measuring diaphragm of the pressure transmitter under the working condition of the coal gasification device is more important.
If you cannot find an answer to your question in our Industrial Gas Pressure Sensors and Transducers, you can always contact us and we will be with you shortly.
More Gas Measurement Solutions
Sino-Inst is a manufacturer of Industrial Gas Pressure Sensors and Transducers. We offer more than 50 types of Gas Pressure Sensors.
Industrial Gas Pressure Sensors and Transducers are used in hydraulic and pneumatic control systems, thermoelectric units, constant pressure water supply systems, power station operation inspections, petrochemical, environmental protection, air compression, locomotive braking systems, light industry, mechanical metallurgy, building automation, and other automation And testing systems, industrial process testing and control, laboratory pressure calibration, etc.
Sino-Inst’s entire team is well trained, so we can ensure that each customer’s needs are met. If you need any help with your product requirements, whether it is Industrial Gas Pressure Sensors and Transducers, level sensors, or other equipment, please give us a call.
Request a Quote
Wu Peng, born in 1980, is a highly respected and accomplished male engineer with extensive experience in the field of automation. With over 20 years of industry experience, Wu has made significant contributions to both academia and engineering projects.
Throughout his career, Wu Peng has participated in numerous national and international engineering projects. Some of his most notable projects include the development of an intelligent control system for oil refineries, the design of a cutting-edge distributed control system for petrochemical plants, and the optimization of control algorithms for natural gas pipelines.