Pressure transmitters are among the most widely used instruments in industrial automation. Whether you’re working in oil and gas, water treatment, pharmaceuticals, or manufacturing, pressure measurement is fundamental to safe and efficient operations.
But here’s where many engineers—especially early in their careers—get tripped up: not all pressure transmitters measure pressure the same way. Choosing the wrong type can lead to inaccurate readings, process instability, or even safety risks.
In practice, pressure transmitters are classified based on how they reference pressure and how they are applied in the field. This guide walks through the major types, how they work, and when to use each—based on real-world engineering logic rather than textbook theory.
Understanding Pressure Transmitters
A pressure transmitter is an instrument that measures pressure in gases or liquids and converts it into a standardized electrical signal—typically 4–20 mA or a digital signal—for use in control systems.
At the core of most transmitters is a sensing element (usually a diaphragm) that deforms under pressure. That deformation is converted into an electrical signal and transmitted to systems such as PLCs or SCADA platforms for monitoring and control.
From an engineering standpoint, pressure measurement always comes down to one question:
“Pressure relative to what?”
That reference point is what defines the type of pressure transmitter.
The four primary categories you’ll encounter in industry are:

• Gauge Pressure Transmitters

• Absolute Pressure Transmitters

• Differential Pressure Transmitters

• Multivariable Pressure Transmitters

Beyond these, there are specialized designs tailored for specific environments and applications.
Gauge Pressure Transmitters
What Is a Gauge Pressure Transmitter?
A gauge pressure transmitter measures pressure relative to atmospheric pressure. In other words, atmospheric pressure is treated as zero.
If a system reads 5 bar gauge (5 barg), it means the pressure is 5 bar above the surrounding atmosphere.
This is by far the most commonly used pressure transmitter in industrial environments.
How Gauge Pressure Measurement Works
Gauge transmitters typically have one side of the sensing element exposed to the process pressure, while the other side is vented to the atmosphere.
The difference between process pressure and atmospheric pressure causes the sensing diaphragm to deflect. That deflection is then converted into an electrical signal.
Typical Applications
Gauge pressure transmitters are used in applications where atmospheric pressure variations are not critical:

• Pump discharge pressure monitoring

• Hydraulic systems

• Air compressors

• Water distribution systems

• HVAC systems

Advantages of Gauge Pressure Transmitters

• Simple and cost-effective design

• Easy to install and maintain

• Suitable for most industrial applications

• Widely available across all pressure ranges

Limitations

• Affected by changes in atmospheric pressure

• Not suitable for vacuum or high-precision measurements

Absolute Pressure Transmitters
What Is an Absolute Pressure Transmitter?

An absolute pressure transmitter measures pressure relative to a perfect vacuum (zero pressure reference).
Unlike gauge transmitters, absolute transmitters are completely independent of atmospheric pressure changes.
How Absolute Pressure Measurement Works
Absolute pressure transmitters use a sealed reference chamber inside the sensor that maintains a vacuum.
The sensing element compares process pressure against this fixed vacuum reference, ensuring stable and accurate readings regardless of external conditions.
Typical Applications
Absolute pressure transmitters are used when precision and stability are critical:

• Vacuum systems

• Barometric pressure measurement

• Semiconductor manufacturing

• Aerospace testing

• Leak detection systems

Advantages of Absolute Pressure Transmitters

• Highly accurate and stable

• Not affected by weather or altitude

• Ideal for vacuum and low-pressure applications

Limitations

• Higher cost compared to gauge transmitters

• More complex design

Differential Pressure Transmitters
What Is a Differential Pressure Transmitter?

A differential pressure (DP) transmitter measures the difference between two pressure points.
It has two process connections: High-pressure side (HP), and Low-pressure side (LP).
The transmitter calculates the difference between these two values and outputs a signal proportional to that difference.
How Differential Pressure Measurement Works
A sensing diaphragm sits between two pressure chambers. When there is a pressure difference, the diaphragm deflects.
This deflection is converted into an electrical signal representing the pressure difference.
Why Differential Pressure Is So Important
From a practical standpoint, DP transmitters are some of the most versatile instruments in process industries.
They are widely used for indirect measurements such as:

• Flow measurement (using orifice plates or venturi tubes)

• Liquid level measurement in closed tanks

• Filter monitoring (detecting pressure drop)

• Density measurement

Typical Applications

• Oil and gas pipelines

• Chemical processing plants

• Water treatment facilities

• Steam flow measurement systems

Advantages of Differential Pressure Transmitters

• Extremely versatile

• Enables indirect measurement of multiple variables

• Essential for flow and level measurement

Limitations

• Requires proper installation on both pressure sides

• Sensitive to clogging or blockage in impulse lines

Multivariable Pressure Transmitters
What Is a Multivariable Transmitter?

A multivariable pressure transmitter goes beyond measuring pressure alone. It can measure multiple process variables simultaneously, typically:

• Differential pressure

• Temperature

• Static pressure

These measurements are then used to calculate additional parameters such as flow.
Multivariable transmitters are widely used in advanced process systems, particularly for gas and steam flow measurement.
How Multivariable Transmitters Work
Instead of using separate instruments, a multivariable transmitter integrates multiple sensors into a single device.
The internal processor calculates flow and other variables using built-in algorithms.
Typical Applications

• Steam flow measurement

• Natural gas flow monitoring

• Energy management systems

• Advanced process control systems

Advantages

• Reduces the number of instruments required

• Improves measurement accuracy

• Simplifies installation and maintenance

Limitations

• Higher initial cost

• More complex configuration

Specialized Types of Pressure Transmitters

In addition to the main categories, several specialized transmitters are designed for specific environments and operating conditions.
Submersible (Hydrostatic) Pressure Transmitters
These transmitters are designed to measure liquid level by sensing hydrostatic pressure.
Applications

• Water tanks

• Reservoirs

• Wells and boreholes

• Wastewater treatment plants

They are fully sealed and built to withstand immersion in liquids.
Wireless Pressure Transmitters
Wireless transmitters eliminate the need for physical wiring by transmitting data via radio or industrial wireless protocols.
Applications

• Remote oilfields

• Pipelines

• Environmental monitoring systems

• Hard-to-access installations

They significantly reduce installation costs and improve flexibility.
Smart (Digital) Pressure Transmitters
Smart transmitters include microprocessors that provide advanced features such as:

• Self-diagnostics

• Remote calibration

• Digital communication (HART, Modbus, etc.)

These are standard in modern industrial automation systems.
High-Temperature and Remote Seal Transmitters
Used in extreme environments, these transmitters include protective features such as diaphragm seals or cooling elements.
Applications

• Boilers

• Steam systems

• Chemical reactors

• High-temperature process lines

Remote seals protect the sensing element from harsh process conditions.
Explosion-Proof Pressure Transmitters
Designed for hazardous environments, these transmitters are built to prevent ignition in explosive atmospheres.
Applications

• Oil and gas facilities

• Chemical plants

• Mining operations

How to Choose the Right Pressure Transmitter
Selecting the right transmitter comes down to understanding your process requirements.
Reference Type

• Need relative pressure → Gauge

• Need true pressure → Absolute

• Need pressure difference → Differential

Application

• Flow measurement → Differential or multivariable

• Vacuum systems → Absolute

• General industrial use → Gauge

Environmental Conditions

• Harsh or corrosive → Remote seal

• Hazardous areas → Explosion-proof

• Remote locations → Wireless

Accuracy Requirements

• High precision → Absolute or smart transmitters

• General monitoring → Gauge transmitters

A good rule of thumb: always start by defining the measurement objective, then choose the transmitter type—not the other way around.

Recommended Related Articles:

• Industrial Automation Fundamentals
• Industrial Communication Protocols
• Industrial Instrumentation Control
• Industrial Sensors & Measurement
• Motion and Process Control
• PLC Programming & Controllers
• SCADA and DCS Systems
• Servo Motors and Motor Drives

Frequently Asked Questions (FAQ)
What are the main types of pressure transmitters?
The main types are:

• Gauge pressure transmitters

• Absolute pressure transmitters

• Differential pressure transmitters

• Multivariable pressure transmitters

Each type is defined by its pressure reference and application.
Which pressure transmitter is most commonly used?
Gauge pressure transmitters are the most widely used because most industrial processes measure pressure relative to atmospheric conditions.
What is the difference between gauge and absolute pressure?
Gauge pressure is measured relative to atmospheric pressure, while absolute pressure is measured relative to a perfect vacuum.
Why are differential pressure transmitters used for flow measurement?
Flow measurement devices such as orifice plates create a pressure drop. Differential pressure transmitters measure that drop and use it to calculate flow rate.
What is a smart pressure transmitter?
A smart pressure transmitter includes digital communication, diagnostics, and calibration features, making it suitable for modern automated systems.
How do I choose the right pressure transmitter?
Choose based on:

• Type of measurement (gauge, absolute, differential)

• Process conditions

• Accuracy requirements

• Environmental factors