Pressure Transducer for Industrial Applications: Selection Guide & Supplier Overview

In industrial automation, automotive manufacturing, medical equipment and many other fields, the pressure transducer (Pressure Transducer) as the core detection element, bear the key task of gas or liquid mechanical pressure into readable electrical signals. Whether it is to monitor pipeline pressure, control equipment operation, or to ensure production safety, it plays an irreplaceable role.

In this article, from the basic definition to the actual application, comprehensively dismantle the core knowledge of the pressure sensor, to help you quickly grasp its working principle, type, application and selection skills, to help you in the actual scene of the efficient use of this key equipment.

What Is a Pressure Transducer?

Pressure transducer is a kind of sensor and measuring instrument that can accurately convert the input mechanical pressure of gas or liquid into electrical output signal.

Its core function is to accurately detect, measure and monitor the applied pressure by means of pressure-sensitive components, and then, with the help of built-in electronic components, to convert this physical pressure information into electrical signals that can be transmitted and analysed, providing a solid foundation for subsequent monitoring and control, data acquisition and other work.

From the physical definition, the pressure is a liquid or gas acting on a unit area of force (calculated as P = F / A), the industry’s common units of pressure are Pascal (Pa), bar (bar), Niu / square millimetre (N / mm²) and pounds / square inch (psi).

In practice, pressure sensors generally use piezoresistive technology, the core piezoresistive element will change the resistance proportionally with the strain (pressure), to achieve the conversion of pressure signals to electrical signals, which is also the industry’s mainstream and mature pressure detection technology.

The Key Components of a Pressure Transducer

The stable operation of a pressure transducer relies on the co-operation of a number of core components, each of which carries out a specific function and is indispensable. The following is a detailed explanation of its main components and their roles:

Sensitive element (Sensing Element): the part in direct contact with the measured substance, the core role is to convert the physical pressure into mechanical or electrical signals, is the ‘core sensing components’ of pressure detection.
Diaphragm: One of the most commonly used sensitive elements, it is a flexible film. When subjected to pressure, the diaphragm will be bent or deflected, and the degree of deflection is proportional to the applied pressure, thus converting the pressure signal into a mechanical deformation signal.
Strain Gauge: Another commonly used sensitive element, made of wire or foil. When subjected to mechanical stress (e.g. deformation transfer of the diaphragm), its resistance value will change, often used in conjunction with the diaphragm, to accurately capture the pressure brought about by the small deformation.
Amplifier: The electrical signals generated by sensitive components are usually very weak and cannot be used directly for subsequent monitoring or control. The role of the amplifier is to amplify this weak signal and convert it into a standard electrical signal that can be used directly.
Output Signal: The final electrical signal processed by the amplifier, which varies in form depending on the design of the transducer and the application scenario, and commonly consists of a voltage, current or frequency signal.

How Does a Pressure Transducer Work?

The working process of a pressure transducer can be divided into five key steps, from pressure application to signal output, the whole process to achieve the precise conversion of physical pressure to electrical signals, as follows:

Pressure Applied: Gas or liquid exerts a force on the diaphragm of the sensor (a thin and elastic film), which is the starting point of the entire pressure detection process.
Mechanical Deformation: The diaphragm will be bent or deflected proportionally according to the size of the applied pressure, the greater the pressure, the greater the diaphragm deformation, and vice versa, the smaller, to achieve the conversion of pressure signals to mechanical deformation signals.
Electrical Charge: Sensitive components connected to the diaphragm (e.g. strain gauges, piezoelectric crystals, capacitive plates, etc.) accurately capture this small deformation and convert it into a change in electrical characteristics, such as a change in resistance, charge or capacitance.
Signal Conversion: The sensor’s internal electronics will process this small change in electrical characteristics and convert it into a standardised electrical output signal, commonly voltage signals, 4-20mA current signals and digital signals.
System Output: The converted standard signal will be transmitted to the display, controller or data acquisition system, the staff can use these devices for real-time pressure monitoring, recording, or for automatic control of equipment.

The Electrical Output of Pressure Transducers

The electrical output of pressure transducers is mainly divided into three types, different types of output signals are suitable for different application scenarios, and choosing the right type of output is the key to ensure the accuracy of detection. The following is a detailed description of the three types of outputs and their application scenarios:

Millivolt Output

Millivolt output pressure sensors are the most economical, with a nominal output voltage of about 30mV. The output signal is directly related to the excitation voltage and needs to be matched with a regulated power supply to ensure signal stability.

Due to the weak output signal, millivolt output sensors are more sensitive to electromagnetic interference, and should not be installed in a large electrical noise environment; at the same time, the distance between the sensor and the reading instrument should be shortened as much as possible to avoid signal attenuation.

Voltage Output

Voltage output sensor built-in signal conditioning circuit, the output voltage is much higher than the millivolt output, common standards for 0-5Vdc or 0-10Vdc, the output signal is usually not dependent on the excitation voltage (specific reference model), no regulated power supply, the power supply in the specified range can be.

Due to the higher output signal strength, voltage output sensors are more resistant to electromagnetic interference, suitable for industrial environments and other noisy scenarios, a wider range of applications than millivolt output sensors.

4-20mA current output (4-20mA Output)

This type of sensor, also known as pressure transmitter, its 4-20mA current signal is the most commonly used output type in the industrial field, strong anti-interference ability, not affected by line resistance, suitable for long-distance transmission and can ensure signal stability and accuracy.

It should be noted that, regardless of the choice of output type, the final electrical output signal needs to be converted to PSI, bar and other engineering units, in order to achieve intuitive reading and analysis of pressure.

Types of Pressure Transducers

According to the different measurement techniques, pressure transducers can be divided into a variety of types, each type has its own unique working principle and applicable scenarios, the following are the most common 6 types:

Strain Gauge Pressure Transducer

Suitable for measuring very high and low pressures as well as differential pressures (pressure difference between two points). At its core is a sensitive element with a diaphragm, which, when deformed, drives a change in the resistance of the strain gauge.

In practice, a Wheatstone bridge structure with four strain gauges is used to maximise the detection sensitivity of the sensor, and ultimately the change in resistance of the strain gauges is converted into an electrical output signal that can be used directly for monitoring and control.

Capacitance Pressure Transducer

Capacitance pressure transducers measure pressure by detecting changes in capacitance, and their core structure consists of a diaphragm (acting as a capacitive pole plate) and electrodes (acting as another capacitive pole plate) fixed to a non-pressurised surface.

When the pressure changes, the diaphragm will be deflected, resulting in a larger or smaller gap between the two plates, which in turn changes the capacitance value, which is then converted into a standard electrical signal by the electronic components. They can be used to measure absolute, gauge or differential pressure and are flexible in their application.

Potentiometric Pressure Transducer

Consisting of a precision potentiometer, the sliding piece of the potentiometer is connected to a pressure sensitive element (e.g. a diaphragm). When the diaphragm is deflected by pressure, it will drive the sliding piece to move and change the resistance value between the sliding piece and one end of the potentiometer, which is the corresponding value of the measured pressure. The structure is simple, low cost, and suitable for scenes that do not require high accuracy.

Resonant Wire Pressure Transducer

The core of the transducer is a vibrating wire fixed on the diaphragm, and an electronic oscillator maintains the continuous vibration of the wire. When the diaphragm deforms due to a change in pressure, the tension of the wire changes, which in turn changes its resonant frequency. The frequency change is detected by a digital counting circuit and converted into an electrical signal, which provides high measurement accuracy and is suitable for high-precision pressure measurement.

Inductive Pressure Transducer

Based on the principle of electromagnetic induction, the diaphragm is connected to a ferromagnetic core. When the diaphragm is deflected slightly by pressure, the ferromagnetic core moves linearly and induces a change in current in the inductive coil. Pressure variations cause the core to move different distances, and the induced current varies, which is then converted into a usable electrical signal.

Piezoelectric Pressure Transducer

Piezoelectric pressure transducers rely on the piezoelectric effect of quartz crystals or ceramic materials: when pressure is applied to the surface of these sensitive materials, the material generates an electrical charge proportional to the pressure applied, which is converted into a stable voltage signal after signal conditioning.

This type of sensor is extremely sensitive and responsive, and can accurately capture fast-changing pressure signals, especially suitable for real-time monitoring of dynamic changes in pressure.

10 Applications for Pressure Transducers

Pressure transducers are used in almost all fields that require pressure detection, from industrial production to daily life, from ordinary scenes to special environments, all can see its figure. The following are the 10 most common application scenarios, with a detailed analysis of how they are used in practice:

Water level measurement in water tanks

There are various ways to realise this:

Using a submersible pressure sensor, fixed to the bottom of the tank by a submersible cable, the pressure of the water in the tank is measured, which is then converted to the height of the water level;
In open systems, a gauge pressure sensor is mounted at the bottom of the tank or on the outlet pipe and the water level is calculated indirectly by measuring the weight of the water;
in closed systems, a differential pressure sensor is used to measure the pressure difference between the top of the tank and the liquid to achieve water level monitoring.

Water Pipe Leakage Detection

Multiple pressure sensors are installed on underground or above ground pipes. When a pipe ruptures or leaks, the sensors around the leakage point will be the first to detect the largest pressure drop, thus pinpointing the location of the leak. In addition, wireless pressure sensors can real-time remote monitoring of leaks, effectively improving detection efficiency and reducing the cost of manual inspection.

Gas Leak Detection

Taking the preset reference pressure as the benchmark, the gas pressure entering the tank is dynamically monitored in real time to ensure that the pressure inside the tank is always maintained within the safe rated range.

Once a leak occurs in the gas storage tank, the pressure inside the tank will drop abnormally, and the sensor will quickly capture this pressure change and boost the output signal simultaneously, thus quickly locking the leakage hidden danger, effectively avoiding safety risks, and safeguarding the operation safety of the gas storage equipment and the surrounding environment.

Gas Pressure Monitoring

For non-flammable gases, the pressure sensor can be used to monitor the pressure change inside the gas storage tank in real time, and at the same time capture the effect of ambient temperature fluctuations (such as sun exposure, cold weather) on the gas pressure inside the tank to ensure that the pressure is in a reasonable range;

For flammable gases, it is necessary to use pressure sensors equipped with explosion-proof shells or specialised pressure sensors for hazardous environments with professional safety certification, to avoid safety hazards from the level of equipment and to ensure the safety and reliability of the whole monitoring process.

Pump Pressure Measurement

According to the size of the pump to choose the appropriate pressure sensor: small pumps need to use miniature pressure sensors, large pumps can use ordinary pressure sensors. It should be noted that large pumps may produce water hammer effect during operation, easy to damage the sensor, so the sensor can be installed in the pump downstream, so that the pump force tends to stabilise before testing.

High Temperature Environmental Pressure Measurement

In the need to measure the pressure of high temperature gas or fuel in the scene, ordinary pressure sensors will be due to high temperature expansion of internal components, resulting in measurement errors or even damage. In this case, the siphon effect is used:

The sensor is moved away from the measurement area, allowing the liquid or gas to dissipate heat through a section of metal piping before entering the sensor for detection. The thicker the metal pipe, the shorter the distance between the sensor and the measuring area.

Flow Monitoring

Differential pressure sensors are one of the most commonly used devices for measuring flow. The principle is to form a pressure drop in the pipe by means of a throttling element (e.g., orifice plate, venturi), which is detected by the differential pressure sensor, which then calculates the flow rate of the fluid in the pipe according to the correspondence between the pressure drop and the flow rate.

Baghouse Pressure Measurement

In a factory baghouse, differential pressure sensors are used to measure the pressure difference between the two sides of the filter bag. As more particles are collected by the filter bag, the filtration resistance increases and the pressure difference between the two sides rises. When the pressure difference reaches a certain threshold, it indicates that the filter bag is clogged and needs to be replaced in a timely manner to ensure effective dust removal.

R&D Test Applications

In the automotive, aerospace and other manufacturing industries, pressure sensors are widely used in test benches to accurately measure the water pressure, fuel pressure, air pressure and other key parameters of automobiles, aircraft and other products, to provide accurate and reliable data support for product research and development, performance testing and quality optimisation, and to help improve the core performance of the product.

Food and Beverage Industry Pipeline Pressure Maintenance

In the food, beverage, brewing, dairy and other industries, the use of sanitary pressure sensors to monitor the pressure of the filling line, to ensure the normal operation of the filling equipment, while avoiding abnormal pressure caused by product leakage or packaging damage. Sanitary sensors also need to meet the requirements of easy to clean, no bacterial growth, to adapt to industry hygiene standards.

Supplementary: High Temperature Steam Pressure Measurement

Ordinary pressure sensors are typically used at temperatures between 51°C and 93°C, and are not suitable for high-temperature steam environments. Pressure transducers for high-temperature steam use piezoelectric cores that can withstand high temperatures, and some models can measure steam pressure at temperatures above 1000°C. However, these transducers are typically used for short-term measurements only, and need to be cooled down at regular intervals to avoid damage from overheating.

Advantages of Pressure Transducers

The core reason why pressure transducers can be widely used is that they have a number of outstanding advantages to meet the needs of different scenarios:

Excellent economy: the use of mature and stable manufacturing process, mass production costs can be controlled, cost-effective, can be adapted to different budget scenarios, taking into account the purchase cost and detection needs, without the need to pay extra for redundant functions.
Excellent stability: Relying on precision circuitry and high-quality components, it can output stable standard electrical signals, suppress signal fluctuations, reduce measurement errors, and ensure accurate data in long-term operation, providing reliable support for equipment control and data analysis.
High sensitivity: miniaturised design, compact size, flexible installation, suitable for space-constrained scenarios; sensitive response of the core sensitive components can accurately capture small pressure fluctuations to meet the demand for high-precision measurement.
Strong practicality: simple structure, easy to mass production, shell and components after special treatment, durability, can withstand industrial complexity interference, can be in the harsh environment of long-term stable operation, suitable for multi-industry and multi-scene, reduce failure and maintenance frequency.

Disadvantages of Pressure Transducers

Despite the significant advantages of pressure transducers, there are some limitations in practical applications that need to be avoided in advance:

There is a drift phenomenon, affected by component aging, temperature fluctuations, power supply instability and other factors, will reduce the measurement accuracy, can only provide medium accuracy results, can not meet the high-precision core scenarios, need to be calibrated periodically to ease the error.
Slow response to shock and vibration, due to the delay in the mechanical response of the sensitive components and circuit signal processing, in the rapid fluctuation of pressure scenes are prone to signal lag, data distortion, affecting the real-time control of equipment.
Ordinary pressure sensors are not suitable for high-temperature environments, high temperatures will lead to component precision degradation, accelerated aging or even damage, the need to use special high-temperature type sensors.
Anti-interference ability is limited, susceptible to electromagnetic interference, humidity changes in the industrial environment, resulting in signal fluctuations, precision degradation, need to take the installation of shielding, sealing and other protective measures.

Why Is It Important to Calibrate Pressure Transducer?

Calibrating a pressure transducer is the process of adjusting and correcting the transducer or its amplifier to ensure that the transducer’s measurements are as accurate and error-free as possible.

The core reason why calibration is necessary is that all transducers have measurement errors that can affect the reliability of the data measured, which in turn affects equipment control and production safety.

Common types of measurement errors and their causes are listed below:

Zero offset (Zero Offset): sensor output signal at zero pressure deviates from the ideal value, zero stability refers to its unchanged environment to maintain the zero balance of the ability to zero offset will lead to the measurement of the reference error.
Non-linearity (Linearity): Ideally, the output signal of the sensor and the input pressure should be linear (doubling the pressure, the output is also doubled), but in practice there are few sensors can achieve complete linearity. Non-linearity error is the maximum deviation between the actual calibration curve and the ideal straight line, usually expressed as a percentage of the rated output.
Hysteresis: The maximum difference between the sensor’s output reading at the same pressure as the pressure rises from zero and the output reading as the pressure falls from the rated value, usually measured at half the rated output and expressed as a percentage of the rated output. Measurements need to be taken quickly to minimise errors due to creep.
Repeatability (Repeatability): refers to the same pressure and environmental conditions, the sensor to repeat the input of the maximum difference between the output readings, reflecting the consistency of the sensor to repeat the measurement, poor repeatability will lead to large fluctuations in measurement data.
Temperature drift (Temperature Shift): refers to changes in the output signal and zero balance due to changes in sensor temperature, temperature drift will be amplified in extreme temperature environments, seriously affecting the measurement accuracy.

Calibration requires comparing the sensor output with the standard reference pressure by means of calibration equipment, adjusting the response curve, correcting errors such as zero offset and hysteresis, etc. Critical scenarios also require additional testing of repeatability and temperature drift to ensure high-precision measurement requirements.

Proper Pressure Transducer Installation

Proper installation is the key to proper pressure transducer performance and extended service life, as well as reducing measurement errors and avoiding equipment damage. The following are the 8 core installation steps and precautions:

Choose a suitable installation location: the installation location should meet the needs of accurate pressure measurement, and should be away from excessive vibration, high temperature and humidity, to effectively avoid the adverse effects of environmental factors on the performance of the sensor, to ensure the stability of detection.
Matching pressure range: Make sure that the pressure measurement range of the sensor matches the actual pressure of the system to prevent damage to the sensor when the pressure exceeds the range, and also to avoid attenuation of the measurement accuracy due to low pressure, so as to guarantee the accuracy of the data.
Use the appropriate connector and thread: the pressure interface and thread type should be accurately matched with the system connecting parts to ensure a tight connection and no leakage, to prevent the pressure measurement deviation caused by leakage problems, to ensure the accuracy of the test results.
Avoid pressure shocks: If there are sudden pressure fluctuations (i.e. pressure spikes) in the system, a pressure buffer or damper should be installed to effectively cushion the pressure shocks, reduce the risk of damage to the sensors, and prolong the service life of the equipment.
Installation in the correct direction: Strictly follow the manufacturer’s installation direction requirements, especially in liquid or gas measurement scenarios, the wrong direction of installation will easily lead to media residue, which will lead to measurement errors and affect the detection effect.
Correct wiring: connect the power supply and signal lines in accordance with the wiring diagram of the equipment to ensure that the wiring is accurate and firm, to avoid signal anomalies and sensor damage caused by wiring errors, and to ensure the normal operation of the equipment.
Check for leaks: After the installation is completed, all connection parts should be carefully checked to make sure there is no pressure leakage. Leakage will not only lead to distortion of the measurement data, but also may lead to safety hazards, affecting the safety of production and operation.
Post-installation test: The output signal of the sensor needs to be verified to confirm that the equipment works properly, the measurement data is accurate, and the problems caused by improper installation should be investigated in a timely manner to avoid subsequent operational failures.

Pressure Transducer Selection Criteria

Selection of the appropriate pressure transducer can ensure the reliability and accuracy of data acquisition, to avoid equipment damage or measurement errors caused by improper selection. Selection should focus on the following 12 core parameters, combined with the actual application scenarios comprehensive judgement:

Pressure range

Refers to the maximum and minimum pressure that the sensor can accurately measure, the selection should focus on two points:

Accuracy requirements: To ensure the best accuracy, the normal operating pressure should be in the middle of the sensor’s measuring range;
Overpressure protection: the need to consider the system may be abnormal pressure (such as valve failure caused by pressure surges), select the sensor with sufficient overpressure protection to avoid pressure out of range damage to the equipment.

Example: the normal operating pressure of a hydraulic system is 2000psi (137.8bar), the selection should be selected around the 2000psi measurement range of the sensor (such as 1500-2500psi), while ensuring that the overpressure protection capacity of more than 3,000psi (such as 4,000psi), to cope with the pressure surge scenario.

Connection Size and Voltage

Connection size should be matched with the existing components of the system to ensure a solid connection and no leakage; the voltage range should be compatible with the power supply system to avoid mismatch of voltage that may cause the sensor to fail to work properly. Also, make sure that the thread size of the sensor matches the equipment or connector to further eliminate leakage.

Linearity

Linearity refers to the degree of linear correspondence between the output signal of the sensor and the input pressure, and its non-linear error is usually expressed as a percentage of the rated output (e.g., 0.2%-0.5%). In general, the lower the non-linearity error, the higher the measurement accuracy of the sensor, so in core applications such as aerospace and pharmaceuticals, where measurement accuracy is critical, it is important to prioritise sensors with excellent linearity.

Process Media

The part of the sensor in direct contact with the fluid (wet end) needs to be compatible with the process medium to avoid corrosion or contamination. Recommendations for common media:

For corrosive fluids (such as seawater), it is recommended that the use of high nickel alloy material sensors, can effectively resist corrosion of the medium, to protect the long-term stable operation of the equipment;
For common application scenarios, the choice of 304, 316 stainless steel or 17-4 stainless steel material can be, taking into account the corrosion resistance and economy;
Food, beverage, pharmaceutical and other health industries, need to use special sensors with sanitary connectors, easy to daily cleaning and disinfection, to prevent bacterial growth, strict compliance with industry health standards.

Output Type

According to the transmission distance and environmental noise selection:

Short distance, no electromagnetic interference scene: give priority to millivolt (mV/V) output type, its cost is the most economical, can meet the basic detection needs;
Industrial complex environment, medium distance signal transmission scene: choose amplified voltage output (0-5V/0-10V) type, with strong anti-electromagnetic interference ability, suitable for most industrial monitoring needs;
Long-distance signal transmission scenarios: choose 4-20mA current output type, signal transmission is stable and no attenuation, which is the best choice for industrial long-distance monitoring;
Scenarios that need to be interfaced with digital systems: choose the digital output type, which can be directly interfaced with computers, digital controllers and other equipment, without additional signal conversion, to enhance the efficiency of data transmission;
Scenarios with unstable power supply: choosing the proportional output type can effectively avoid the influence of power supply fluctuation and ensure the stability of output signal accuracy.

Application and Measurement Type

Select the appropriate pressure measurement type according to the measurement requirements:

Absolute pressure: Measure the total fluid pressure (including atmospheric pressure) based on perfect vacuum;
Gauge pressure: Measurement of pressure above or below atmospheric pressure with reference to ambient atmospheric pressure;
Differential pressure: measurement of the pressure difference between two points within a system;
Vacuum pressure: measures pressure below atmospheric pressure, applicable to suction equipment;
Bidirectional pressure: can measure both positive and negative pressure, applicable to scenarios where pressure fluctuates in both directions.

Temperature range

Choose a sensor that matches the temperature of the working environment. For high temperature scenarios, it is recommended to choose thin-film technology sensors, whose material is more resistant to high temperature and less likely to cause measurement errors due to thermal expansion and contraction. Note that extreme temperatures can lead to output errors (usually expressed in %FS/°C), the larger the error, the more pronounced the effect of temperature on measurement accuracy.

Accuracy

Refers to how close the sensor’s measured value is to the true pressure value, usually expressed as a percentage of the rated output. For common scenarios (e.g., general pipeline monitoring), 0.5% accuracy is sufficient, while core scenarios (e.g., semiconductor manufacturing, medical equipment) require a higher accuracy sensor.

Resolution

Refers to the smallest pressure change that the sensor can detect. The higher the resolution, the better it can capture small pressure fluctuations. High-precision measurement scenarios (e.g., R&D testing) require the selection of high-resolution sensors, while ordinary inspection scenarios can choose low-resolution sensors to reduce costs.

Response time

Refers to the response speed of the output signal after the sensor detects a pressure change. Real-time monitoring scenarios (such as medical ventilators) need to choose fast response time sensors, slow pressure change scenarios (such as water tank level monitoring) can choose slower response time sensors, more cost-effective.

Installation Environment

Need to consider the environment of corrosive and explosive vapours:

Corrosive environment: choose corrosion-resistant housing sensors to avoid housing damage;

Explosive vapour environment: choose explosion-proof housing or intrinsically safe sensors to ensure the safety of use, intrinsically safe sensors will be powered to control the power supply will not ignite the flammable gas range.

Conclusion

In practical applications, it is necessary to choose the appropriate pressure sensors according to the specific system requirements, focusing on the consideration of the pressure range, output signal type, media compatibility and environmental conditions and other core factors. At the same time, standardized installation and regular calibration is indispensable to ensure long-term stable operation of industrial monitoring and control systems, to ensure that the measurement accuracy of the key to meet the standard.

If you are looking for a professional supplier of industrial pressure sensors, or have OEM/ODM customization needs related to HVAC, refrigeration and automation systems, we will provide you with reliable sensing solutions that fit all kinds of application scenarios.