Pressure Transducers – Types, Applications, and How They Work

Pressure transducers are critical components used for measuring gasses or liquids in industrial, automotive, medical, and other industries. They are vital for maintaining the safety, efficiency, and performance of systems that rely on precise pressure control. In this article, we’re taking an in-depth look at the different types of pressure transducers, their working components, how they work in applications, and more.

A pressure transducer is a critical device that measures pressure in gasses or liquids to give accurate and reliable pressure readings in applications. A common example of an application that relies on pressure transducers is the heart rate monitors used in doctors' offices. Pressure transducers (sometimes called a sensor pressure transducer, a pressure sensor transducer, or a pressure transmitter) convert pressure into an electrical or digital signal transmitted and read by other devices, such as controllers, computers, or displays

A pressure sensor transducer typically works in a continuous state, meaning it is always sensing or measuring pressure when connected to a system and powered. Therefore, if the pressure changes in a system or application, the pressure transducer immediately detects the change. What does a transducer do, i.e., how does it sense the change? The pressure transducer sensor (i.e., the sensing element) translates the pressure into an electrical or mechanical signal, sending it to a display, controller, or data acquisition system. This process allows for real-time monitoring and control.

It’s helpful to identify the working components of a pressure transducer to fully understand how it works.

The sensing element is a core component of pressure transducers. It reacts to pressure changes, facilitating signal transmission within the pressure transducer. Sensing elements are typically made of silicon, metal, or ceramics. The following are the three most common types of sensing elements used.

• Diaphragm: a thin, flexible membrane that deforms when pressure is applied.
• Strain gauge: a device that changes resistance when deformed by pressure.
• Piezoelectric crystal: a material that generates a voltage when mechanically deformed.

When the sensing element reacts and is deformed, it produces a small signal that needs to be amplified by the pressure transducer’s signal conditioning circuitry (i.e., amplifiers, filters, and analog-to-digital converters) to produce a usable output signal.

The pressure transducer’s processed signal (typically voltage, current, etc.) is sent through the output signal interface, translating it into a format that other systems can use for monitoring or control.

There are many types, so exploring each can be timely. Therefore, this section will detail types of pressure transducers using two main categories: the type of pressure measurement they make (i.e., pressure measurement) and the technology or mechanism the transducer uses to measure pressure (i.e., sensing technology).

Pressure transducers use three main measurement modes: absolute, differential, and gauge. 

Absolute Pressure Transducers

These pressure transducers measure pressure relative to a perfect vacuum. Therefore, the reference point is zero (i.e., a vacuum), with one side of the sensor exposed to the medium to be measured and the other sealed to create a vacuum. For example, absolute pressure transducers are used in aircraft altimeters to measure atmospheric pressure relative to a vacuum. As altitude increases, the atmospheric pressure decreases—and by measuring this pressure, the altimeter calculates the aircraft's altitude.

Differential Pressure Transducers

A differential pressure sensor measures the difference between two pressures. Thus, the pressure difference causes a change in the capacitance, which is measured. Differential pressure transducers are essential in applications that require the measurement of pressure differences, like monitoring filters in water treatment plants or measuring fluid flow rates in industrial processes.

Gauge Pressure Transducers

A gauge sensor pressure transducer measures pressure relative to atmospheric pressure. Therefore, one side connects to the system, and the other opens or vents to the atmosphere. Gauge pressure transducers are common in applications where pressure relative to atmospheric pressure is important, like tire pressure monitoring and HVAC systems.

Pressure transducers use various sensing technologies, including capacitive, strain gauge-based, and piezoelectric.

Capacitive Pressure Transducers

Capacitive pressure transducers convert pressure into an electrical signal by measuring changes in capacitance. Therefore, when pressure is applied, the diaphragm moves and changes the capacitance, which is measured and converted into a pressure reading. These types of pressure transducers are common in industrial equipment using hydraulic systems and high-pressure testing.

Strain Gauge Pressure Transducers

This type of pressure transducer measures the pressure of fluids and gasses using strain gauges attached to the diaphragm. The diaphragm deforms when pressure is applied, causing a change in the electrical resistance of the strain gauges, which is then measured and converted into a pressure reading. Strain gauge pressure transducers are also commonly used in hydraulic systems for industrial machinery.

Piezoelectric Pressure Transducers

These pressure transducers use piezoelectric materials, like quartz, that generate an electrical charge on the surface when pressure is applied. The amount of charge it produces is directly proportional to the amount of pressure applied. Therefore, the stronger the pressure, the more electrical charge is generated. Piezoelectric pressure transducers are used to monitor pressure changes caused by vibrations in jet engines, which helps assess engine performance and detect potential issues.

Peerless Electronics is an authorized stocking distributor for many leading manufacturers and suppliers within the military, aerospace, industrial, transportation, and medical sectors. We stock high-quality pressure transducers from respected manufacturers like Danfoss, Inc. and Honeywell AST. Every Peerless purchase includes over 50 Value-Added Services designed to save time, maintain workflow, and lower costs.

Pressure sensors and transducers are essential in many fields where accurate and reliable pressure measurement is critical for safety, efficiency, and performance. The following are examples of applications across several industries.

• Hydraulic System Monitoring: pressure transducers are used to monitor pressure in hydraulic systems, like those used in lifts and manufacturing equipment.
• Process Control in Chemical Plants: pressure transducers monitor pressure in reactors, tanks, and pipelines involved in the manufacturing processes.
• Filter Monitoring in Water Treatment: differential pressure transducers are used to measure the pressure drop across filters in wastewater and water treatment facilities.

• Altitude Measurement: aircraft altimeters use absolute pressure transducers to measure atmospheric pressure and determine altitude for navigation and flight control.
• Cabin Pressure Control: differential pressure transducers measure the pressure difference between the aircraft cabin and outside to control cabin pressurization.
• Engine Performance Monitoring: jet engines use gauge pressure transducers to measure pressures (e.g., fuel and oil pressures).

• Tank and Vehicle Pressure Monitoring: these vehicles use pressure transducers to monitor fuel system and hydraulic pressures.
• Submarine Pressure Control: subs use differential pressure transducers to monitor and control pressure in ballast tanks.
• Missile Propulsion Systems: high pressure transducers help monitor the pressure in rocket and propulsion systems.

• Blood Pressure Monitoring: blood pressure monitors (manual and automated) use pressure sensor transducers to measure blood pressure in arteries.
• Respiratory Support Systems: pressure transducers monitor the pressure of air delivered to patients’ lungs in ventilators.
• Intracranial Pressure Monitoring: digital pressure transducers help measure the pressure in the skull, essential for monitoring patients with traumatic brain injuries and other conditions. 

What is the pressure transducer symbol?

In standard electrical schematics, it’s commonly a box or rectangle with an arrow pointing toward it to indicate pressure measurement.

What factors should I consider when selecting a pressure transducer for my application?

Factors to consider include the pressure range, output signal, accuracy, environmental conditions, and temperature when selecting the appropriate pressure transducer.

Why is pressure transducer calibration important?

It’s important to maintain the component’s performance and accuracy by verifying and adjusting the pressure transducer with routine and post-event calibrations (e.g., extreme temperatures, overpressure).