The pressure transmitter is essential for pressure measurement in various industrial sectors. The pressure transmitter detects pressure and converts it into an electrical signal...
The pressure transmitter is essential for pressure measurement in various industrial sectors. The pressure transmitter detects pressure and converts it into an electrical signal, enabling precise monitoring and regulation of pressure in industrial processes.
The pressure transmitter industrial ATEX SIL 2 SIL 3 for liquid, gas and steam. Continuously measures pressure, flow, level and density. Available in ATEX.
Fuji Electric improves its pressure transmitters with the latest technological innovations. Discover our comparative table of old and new references for a simplified transition and optimal performance.
Buyer's Guide to Pressure Sensors and Transmitters
The pressure transmitters are indispensable in various industrial and technological applications.
From the origin and unit of measurement of pressure to the advantages and disadvantages of different types of sensors, you will discover what a pressure transmitter is, how it works, and how a pressure transmitter operates.
We will also detail the composition of a pressure transmitter, the types of output signals, and the essential criteria for choosing an industrial pressure transmitter . By exploring the different categories of pressure transmitters differential pressure transmitter , absolute pressure transmitter , and gauge pressure transmitter — we will guide you on how to calibrate, install, and test them effectively.
Finally, we will look at pressure transmitter configuration and the practical applications of this essential field instrument, weighing up its advantages and disadvantages.
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Pressure transmitters for pressure, flow, level, and density measurement
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The Pascal unit of measurement is named after the renowned French philosopher, physicist and mathematician : Blaise Pascal.
Born in Clermont-Ferrand, where the production unit of Fuji Electric France SAS, a French manufacturer of industrial pressure transmitters , is headquartered, Pascal carried out a fundamental experiment by transporting a barometer to the summit of the Puy de Dôme, to prove that atmospheric pressure decreases with altitude above sea level.
However, Italian scientist Evangelista Torricelli was the pioneer in demonstrating the pressure exerted by the weight of the volume of air on the earth and designed the first mercury-based barometer.
Pressure measurement unit
Thep is expressed in units of force F per unit area A: p = F / A
If we refer to the definition of a pressure transmitter, it is a pressure sensing device whose principle consists in converting the force applied by the pressure of a fluid on a given surface (deformation) into an electrical signal.
Industrial companies use pressure transmitters to :
Measure pressure with a gauge pressure or absolute transmitter.
Flow measurement with a primary element and a differential pressure transmitter
Measuring level with hydrostatic pressure transmitter
Measuring density with a differential pressure transmitter
How does a pressure transmitter work?
The fluid pressure is applied to an internal measuring component via a fitting and then a mechanical interface - measuring diaphragm made of stainless steel, ceramic or another noble material.
The electronic measuring element converts the pressure into a raw output signal.
How does a pressure transmitter work?
There are different technologies, methods, techniques and measurement principles for pressure transmitters models, each adapted to specific applications in the fields of process automation and industrial plants.
The piezoresistive pressure transmitter measures the force applied to a metal membrane. The stress exerted on a thin film causes it to deform, transmitting the pressure variation via an incompressible fluid (oil or water). This fluid deforms a piezoresistive silicon element (Wheatstone bridge circuit). This component, which uses semiconductors, is a variable electrical resistor that converts the deformation into an ohmic value. MEMS (Micro-Electro-Mechanical Systems) are also used in some of these sensors, offering miniaturization and greater sensitivity.
The capacitive pressure transmitter measures the force applied to a stainless steel or ceramic metal membrane. The pressure exerted deforms the metal film, which transmits the pressure variation via an intermediary incompressible fluid (oil or water). This deforms a capacitive silicon element. This component is a variable capacitor which converts the deformation into a capacitive value.
The frequency resonance transmitter uses specific terms such as BFSL (Best Fit Straight Line) to define the linearity of the measurement. This pressure transmitter converts pressure variation into a change in oscillation frequency, offering high resolution and a variety of solutions for different applications.
The strain gauge or voltage gauge pressure transmitter works in a similar way, where the sensor output signal is then filtered, amplified, temperature-compensated and formatted into an analog signal. The analog output is transmitted via an electrical connector, reducing errors and improving accuracy.
Pressure gauges, on theother hand, feature a local display of the pressure measurement.U-tube manometers, for example, are often used for simple, direct measurements.
Construction of the pressure transmitter
The construction of a pressure transmitter comprises several essential elements:
a mechanical connector for mounting,
a metallic or ceramic membrane,
a capacitive sensor or piezoresistive detector,
a filling fluid, often oil, integrated into the pressure cells to transmit pressure variations,
electronic module for conditioning and amplifying the detector signal,
an electrical connector for easy connection to other automation systems,
a plastic or metal housing (aluminum, stainless steel, stainless steel),
a digital indicator (optional) to display pressure information in real time.
Internal cross-section of a pressure transmitter the measuring cell and the silicon microcapacitive sensor.
What is the output signal of an industrial pressure transmitter ?
The pressure transmitter can be either analog or digital. The analog signal from pressure transmitter is usually a 4-20mA current output, a 0-10V voltage output or a 1-5V voltage output. The output signal is sent to the control unit in order to act on the control unit.
The 4-20mA analog output signal is commonly used by these devices because of the many advantages it offers.
First, the pressure transmitter 4-20 mA is resistant to signal loss due to the transmission line, ensuring accurate measurement.
It also extends the distance between the pressure transmitter and the system concerned. In addition, the absence of current makes it possible to detect line faults, facilitating troubleshooting. The 4-20mA 2-wire or 4-wire pressure transmitter is also less sensitive to electromagnetic interference, which guarantees its reliability.
Finally, it can be used in a 4-20mA loop to power several devices such as the display, controller and recorder.
Digital communication is available with various communication protocols - HART - Fieldbus - Profibus - Modbus. These communication protocols not only transmit the measured value, but also enable pressure measurement devices to be configured. These are known as SMART electronic pressure transmitters. Some electronic pressure transmitters also offer IO Link interfaces, a range of specific measurement accuracies and ranges, and international approvals.
What are the best industrial pressure transmitters ?
The best industrial pressure pressure transmitter depends on the application, the measurement range, the required accuracy, and the operating conditions. Fuji Electric’s FCX Series pressure sensors and transmitters are designed for demanding industrial applications, including the measurement of differential, relative, and absolute pressure. The choice of model depends on the process characteristics and installation constraints.
Model
Measurement type
Industrial applications
Standard accuracy
Communication
FKC
Differential pressure
Flow and Level Measurement, and Filter Monitoring
±0,065 %
4–20 mA / HART 7
FKG
Gauge pressure
Pressure Monitoring for Gases and Liquids
±0,065 %
4–20 mA / HART 7
FKA
Absolute pressure
Pressure measurement independent of atmospheric pressure
±0,02 %
4–20 mA / HART 7
FKE
Hydrostatic level
Level Measurement in Tanks and Vessels
±0,02 %
4–20 mA / HART 7
FKB
Relative pressure with diaphragm seals
Corrosive, viscous, or high-temperature fluids
±0,065 %
4–20 mA / HART 7
FKD
Differential pressure with diaphragm seals
Level, Flow, and Differential Pressure Measurement in Challenging Fluids
±0,065 %
4–20 mA / HART 7
FKM
Absolute pressure with diaphragm seals
Absolute Pressure Measurement with Process Isolation
±0,2 %
4–20 mA / HART 7
FKP
Relative pressure for direct mounting
Pressure Measurement with Direct Process Connection
±0,1 %
4–20 mA / HART 7
FKH
Absolute Pressure, Direct Mount
Absolute pressure measurement with direct connection
±0,2 %
4–20 mA / HART 7
FKR
Direct-mount high- gauge pressure
Very-high-pressure measurement up to 1,500 bar
±0,065 %
4–20 mA / HART 7
Comparison of Fuji Electric Industrial pressure transmitters
How to choose an industrial pressure transmitter ?
The choice of industrial pressure transmitter depends on the fluid to be measured, the pressure range and the operating conditions of the application and process.
Illustration of the criteria for selecting a pressure transmitter accuracy, speed, and stability.
The properties of the fluid to be measured, such as:air pressure transmitter, gas pressure transmitter ,hydrogen pressure transmitter ,steam pressure transmitter ,waterpressure transmitter , or other liquid, as well as its characteristics (density, viscosity, corrosiveness, etc.).
Process operating conditions: pressure to be measured, static pressure, process temperature, risk of corrosion
Burst pressure must be taken into account when sizing pressure transmitters. Burst pressure corresponds to the mechanical stress limit of the housing, and when this threshold is exceeded, the housing is destroyed, which can cause fluid leakage. Maintaining the pressure within the specified range ensures reliable measurements in accordance with the specifications in the data sheet.
The gauge pressure transmitter measures the gauge pressure the process relative to atmospheric pressure. Atmospheric pressure is measured using a reference cavity inside the transmitter. This pressure decreases as altitude increases.
The differential pressure transmitter uses two separate chambers connected by a flexible membrane. Pressure is measured on each side of the membrane. The differential pressure (dp) is the difference between these two pressures: a reference pressure on the low-pressure side (LP) and a pressure on the high-pressure side (HP). This differential pressure measuring device is used to measure fluid flow in pipes, monitor filter clogging, or calculate pressure drops.
The absolute pressure transmitter compares gauge pressure absolute vacuum. Absolute pressure is always positive. The advantage of this device is that it is not affected by variations in atmospheric pressure thanks to a vacuum reference chamber, thus providing greater accuracy.
Absolute pressure is expressed from gauge pressure by adding 1.013 bar, i.e. p. absolute (bar abs.) = p. relative (bar) + 1.013.
Diagram explaining the difference between absolute pressure, gauge pressure vacuum relative to atmospheric pressure.
A diaphragm seal pressure transmitter separates the process medium being measured from the pressure cell. The diaphragm and contact parts are made of a material resistant to the fluid being measured, and are welded to the base of the pressure cell.
A capillary tube or connecting sleeve provides the link between the separating diaphragm and the pressure cell. This space must be degassed under vacuum, then filled with oil and sealed. The measured pressure exerts a force on the outer surface of the diaphragm. As the diaphragm flexes inwards, it attempts to compress the filling fluid inside the instrument.
This filling liquid is designed to resist compression, so the force is channeled directly to the pressure-measuring cell. The entire operation of a diaphragm seal pressure transmitter is based on Blaise Pascal's principle.
The diaphragm seal pressure transmitter is made from a variety of materials, including stainless steel, titanium, Inconel, Hastelloy, Monel, Tantalum, ceramic and nickel. The materials used depend on the type of application and temperature for which the industrial pressure transmitter is designed.
The pressure transmitter with diaphragm seals is used to measure fluid pressures in the high-temperature range.
Detail of a pressure transmitter with stainless steel membrane and capillary connection.
The hydrostatic level transmitter is a measuring device used to determine the filling level of a liquid in tanks or vessels. The measuring principle is based on hydrostatic pressure, which is the weight exerted by a liquid as a function of the height of the filling column.
The multivariable pressure transmitter
The multivariable pressure transmitter combines differential pressure measurement, absolute pressure measurement and temperature measurement in a single sensor. These products are used in particular for mass flow measurement.
The submersible pressure transmitter
This submersible or hydrostatic pressure sensor can be immersed in a liquid and used to measure the level of a tank or reservoir. The submersible pressure transmitter is generally fitted with a stainless steel diaphragm.
The calibration period is defined by the pressure transmitters manufacturers. Zero and span must be calibrated.
At the factory, to check the linearity of the output signal, accuracy is verified at several points in the pressure range.
Calibration involves applying a defined reference pressure to the sensor's mechanical interface, checking the 4-20 mA output signal and then applying compensation. The sensor can be calibrated using an external adjusting screw, a programming interface or programming software. Pressure transmitter models with display and pushbuttons can be calibrated locally.
In order to carry out the various manipulations, it may be necessary to have an isolating valve or manifold mounted on the pressure transmitter to isolate it from the process.
How to install a pressure measurement system for industry?
Pressure transmitters can be attached to the Primary Elements for DP Flow or to the pipe where the pressure is to be measured, by means of a mechanical process connection.
Special installation precautions must be taken depending on the process pressure and temperature conditions.
The 4-20 mA output signal of this device can be connected to a display system (an industrial digital display, a recorder, a controller, or a supervision system) or to a PLC (automation system for pressure measurement) in order to control a control device and regulate the pressure of a process.
For your own safety, check the pressure transmitter wiring diagram before wiring the field instrument.
If you need help, we recommend that you call in a professional company to install and commission your measuring instrument.
How to test a pressure transmitter?
A pressure transmitter 4-20 mA can be tested by applying a known pressure to the mechanical interface of the pressure sensor and checking the measured analog output signal. If you have a pressure transmitter a display, check the value shown on the indicator.
If your instrument is faulty, you can ask a specialist or one of the manufacturers of industrial sensors to repair it for you.
If repair is not possible, you can replace your old pressure transmitter with a new, more modern model.
How do I configure a pressure transmitter ?
Intelligent digital transmitters with HART protocol can be configured :
using a local programmable digital indicator to set parameters (for pressure transmitters with display)
Pressure transmitter configuration of a pressure transmitter using a HART-compatible portable communicator.
What are the applications for pressure transmitters ?
Understanding why measuring pressure in process industries is important for ensuring safety, optimizing process control, improving energy efficiency, and maintaining the quality of finished products.
The pressure transmitter is used in many industrial applications.
This digital pressure transmitter can detect pressures ranging from a few millibars to several hundred bars. It is therefore essential in a wide range of industries for the automation of production lines and machines.
Gauge or absolute compressed air pressures, water pressures, steam pressures and gas pressures can all be measured.
Applications include differential pressure measurementof liquid flow, gas flow or vapor flow in a pipeline, filter monitoring, liquidlevel measurement in a tank with a flush diaphragm pressure transmitter , fluid density measurement.
Depending on your industry, you need to choose the right measuring instrument for your application and the constraints of your industrial environment.
What are the advantages and disadvantages of a pressure transmitter
Advantages of pressure transmitters
Accuracy and reliability: pressure transmitters offer extremely precise measurements, essential for industrial applications. They increase productivity and reduce costs by providing precise information on the pressure of gases, vapors or liquids.
Resistance to extreme conditions: Even in high-temperature conditions or corrosive environments, such as those encountered in the chemical or oil and gas industries, their operation is guaranteed with exceptional reliability and precision.
Durability and robustness: Housed in stainless steel or aluminum casings, pressure transmitters withstand shock, vibration and hostile environments. They're built to last.
Flexibility of use: Available in a variety of designs and technologies, these sensors cover a wide range of pressure measurement ranges for all fluids, including vacuum and low-pressure applications. Their flexibility makes them suitable for many industries.
Easy installation: With a wide variety of fittings and connectors available, pressure transmitters be quickly and easily integrated into automation systems, minimizing installation errors.
Resistance to overloads and overpressures: Thanks to their high resistance to overload, pressure transmitters withstand extreme pressure peaks, such as those produced by rapidly closing valves or compressed air water hammer.
Precision and reliability
Resistance to extreme conditions
Durability and strength
Flexibility of use
Easy to install
Resistance to overloads and overpressures
Disadvantages of pressure transmitters
Initial cost: The cost of purchasing pressure transmitters can be high, which may represent a significant investment for some industrial companies. The price of a pressure transmitter often reflects its quality and durability. Avoid exotic pressure transmitters brands and opt for a pressure transmitter manufacturer.
Sensitivity to interference: Sensors using semiconductors can be sensitive to electromagnetic interference, which can affect their accuracy. Choose a manufacturer offering pressure transmitter that comply with EMC standards.
Installation complexity: Although many sensors are designed for easy installation, some complex applications may require specific technical skills to ensure optimal performance. Rely on a pressure transmitter manufacturer.
Maintenance under specific conditions: In certain installations, particularly where environmental conditions are extreme, regular maintenance of your pressure transmitter may be necessary to ensure performance. Choose a pressure transmitter manufacturer pressure transmitter a local maintenance service.
Initial cost
Sensitivity to interference
Complexity of installation
Maintenance under specific conditions
Measuring blood pressure cannot be improvised!
Pressure measurement requires the involvement of professionals in the field of instrumentation.
The experts at Fuji Electric, a French manufacturer of industrial pressure transmitters , will guide you and offer you pressure transmitters designed for your most demanding application, to ensure that you get the performance and results you expect, and to avoid errors in your process pressure measurement. So you can enjoy the benefits of pressure transmitter without the drawbacks.
Fuji Electric pressure transmitters are renowned for their high technology, pressure measurement accuracy, wide measurement range, long-term stability, build quality, reliability, durability, technical support, easy return policy and fast delivery service for customers.
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November 12, 2022
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