What Is a Pressure Transducer?

A pressure transducer, also referred to as a pressure transmitter or pressure sensor, is an electronic device that measures the pressure of air, gas or liquid in industrial systems and converts that measurement into an electrical signal. Although these instruments may be small, they use advanced sensing technology to provide accurate and reliable pressure measurements at different stages of a process.

Ashcroft is an industry leader in pressure measurement instrumentation and created this article to provide a basic foundation of information about pressure transducers for those who are new to the technology.

Read on to learn how pressure transducers work, where they are used, the types of pressure they measure, their pressure ranges and accuracy, and the sensing technologies they use.

How does a pressure transducer work?

A pressure transducer works by measuring pressure and converting that measurement into an electrical output signal, such as current or voltage.

Common pressure transducer outputs include:

• 4 to 20 mA (milliamps)
• 0-5 Vdc (voltage direct current)
• 0-10 Vdc
• Millivolt per volt

Figure 1: How a pressure transducer works

Where are pressure transducers used?

Pressure transducers are used in applications that require continuous pressure measurement and monitoring, including systems exposed to extreme temperatures, shock and vibration.

Common applications include:

• HVAC/R equipment
• Food and pharmaceutical plants
• Off-road transportation
• Hydraulics
• Pneumatics
• Semiconductor manufacturing

Figure 2: Industries where transducers are used

What pressure ranges can a pressure transducer measure?

Pressure transducers can measure ranges from as low as 0-0.1 inches of water for low-pressure applications to as high as 72,000 psi for high-pressure applications.

Their precision levels range from ±0.02% to ±2.00% of span. The type of sensor you use, including whether you need a low- or high-pressure sensor, will depend on the requirements of your application.

Figure 3: Transducer/transmitter pressure ranges

What types of pressure can a pressure transducer measure?

Pressure transducers can measure absolute, gauge, vacuum and differential pressure, depending on the sensor design and application.

Absolute Pressure

Absolute pressure uses a perfect vacuum as its reference point. A perfect or total vacuum occurs when air is completely absent, and there is no negative absolute pressure. Because the reference is a perfect vacuum, the measurement does not fluctuate with atmospheric or barometric pressure.

Gauge Pressure

Gauge pressure is pressure measured relative to ambient atmospheric or barometric pressure. Positive gauge pressure is greater than atmospheric pressure.

Vacuum Pressure

Vacuum pressure is pressure below atmospheric or barometric pressure, using ambient pressure as the reference.

Differential Pressure

Differential pressure is the difference in pressure between two points in a system.

Figure 4: Types of pressure measurement  

How accurate are pressure transducers?

Pressure transducer accuracy varies based on the instrument and application, and the level of accuracy required depends on the needs of the process being measured or controlled.

For instance, if you are controlling an isolation room, maintaining specific pressure levels is critical, so a highly accurate transducer may be required. On the other hand, if you are measuring and monitoring a simpler process, such as water level, the application may only require moderate or lower accuracy.

The accuracy of a pressure transducer also depends on whether temperature effects are included in the accuracy specification.

Figure 5: Accuracy chart

Other factors also contribute to overall accuracy and sensor performance. These elements are included in the manufacturer’s accuracy statement.

To learn more about how accuracy is defined and the elements included for pressure transducers and transmitters, read our e-book, Accuracy Statement for Pressure Instruments.

What sensing technologies are used in pressure transducers?

Pressure transducers use different sensing technologies to convert pressure into a measurable electrical signal, and the technology used can affect the instrument’s accuracy and performance.

Here are two technologies commonly found in pressure sensors.

1. Chemical vapor deposition (CVD) thin film sensor technology

Chemical Vapor Deposition (CVD) thin film technology is an advanced sensing technology designed to provide high reliability and performance across mid- to high-pressure applications.

Ashcroft pressure instruments that use CVD sensing technology include:

• S1 OEM Pressure Sensor
• G2 Pressure Transducer
• ZT High-Purity Pressure Transmitter
• ZX High-Purity Pressure Transmitter

These products use CVD sensing technology to achieve precise and consistent pressure measurement.

Watch this video to learn more about CVD technology.

2. Si-Glas™ Silicon Capacitive MEMS technology

Si-Glas™ Silicon Capacitive MEMS is a sensing technology designed to provide precise and consistent measurements in exceptionally low-pressure applications.

Applications for this technology include:

• Airflow measurement
• Aspiration
• Room pressurization control
• Leak detection

The following Ashcroft products use Si-Glas technology for high accuracy, repeatability and stability:

• CXLdp Pressure Transducer

• DXLdp Pressure Transducer 

• ATE-2 Handheld Calibrator 

Watch this video to learn more about Si-Glas™ technology.

Ready to learn more?

Now you know the basics about pressure transducers, including how they measure pressure and convert it into an electrical signal that can be used to continuously monitor and control industrial processes. Depending on the application, these sensors can measure absolute, gauge, vacuum or differential pressure across a wide range of pressures and accuracy requirements.

If you are ready to dig a little deeper, please refer to the related resources below. You can also contact us today to talk to one of our industry experts about specific questions you may have.