Absolute pressure transmitters are indispensable sensors when it comes to precisely measuring atmospheric air pressure. Unlike relative or differential pressure transmitters, they measure pressure relative to absolute vacuum (0 bar) and are therefore independent of environmental influences such as sea level. This is why they are often referred to as precise barometers for technical applications.
Our absolute pressure transmitters are therefore used in weather measurement technology, ventilation and air conditioning technology, and in all pressure-dependent control systems. They deliver highly accurate measurements and, thanks to switchable output signals (0–10 V or 4–20 mA) and selectable measuring ranges, offer maximum flexibility for connection to your control system or building management system.
In this guide, you will learn everything you need to know about how our absolute pressure transmitters work, their typical areas of application, and how to install them correctly—explained in a compact and practical way.
What is an absolute pressure transmitter?
An absolute pressure transmitter, often referred to as a technical barometer, is a transmitter that measures pressure relative to absolute vacuum (0 bar). It converts this physical value into a standardized electrical signal (e.g., 0-10 V or 4-20 mA) that can be processed by control or monitoring systems. The key advantage over relative pressure transmitters is that the measurement is not influenced by fluctuating ambient pressure or mounting height. This enables highly accurate and stable measurement of the true atmospheric pressure.
How does absolute pressure measurement work?
The functioning of an absolute pressure transmitter is based on a fixed reference point: absolute vacuum. Inside the sensor is a hermetically sealed chamber that is empty of air. The atmospheric air pressure acting from the outside deforms a thin membrane that seals this reference chamber. A high-precision, piezoresistive measuring element detects this minimal deformation and converts it into a proportional electrical signal. Since the counterpressure in the reference chamber is always zero, the transmitter provides a pure measurement value that is not influenced by external air pressure fluctuations.
Typical applications for absolute pressure sensors?
Absolute pressure transmitters are indispensable wherever the exact atmospheric air pressure plays a decisive role in process or control quality. In ventilation and air conditioning technology, they are used to compensate for weather-related air pressure fluctuations and thus, for example, to keep the volume flow in ventilation systems constant. Another important field of application is weather stations and meteorological services, which rely on precise barometric data. In addition, they are used in all pressure-dependent control systems in which the ambient air pressure serves as an important correction variable for control purposes in order to ensure consistently high process stability.
Types of absolute pressure transmitters
Our absolute pressure transmitters are available in two practical types, depending on the need for a local measurement display.
The standard version without display is the ideal choice if the measured air pressure is processed exclusively in a central control system or building management system. For applications that require quick checks or diagnostics directly at the installation site, the version with integrated display offers a decisive advantage. It allows the current absolute pressure to be read immediately without additional measuring devices.
Flexibility through configuration: Adjust output and measuring range
A key advantage of our absolute pressure transmitters is their outstanding adaptability to the respective application. Easily accessible DIP switches inside the housing allow you to precisely adjust the device to your requirements without having to order or stock different variants.
Not only can you choose between the voltage-controlled output signal 0–10 V and the current-controlled signal 4–20 mA, but you can also select one of four predefined measuring ranges. This flexibility ensures that the transmitter can be optimally integrated into any existing control and regulation environment and always offers the best possible signal resolution for your application.
Mounting and connecting absolute pressure transmitters
Correct mounting is crucial for the longevity and reliable function of the absolute pressure transmitter. The robust housing is simply attached to a wall or mounting surface with screws. For permanent protection against moisture and to ensure IP65 protection, the device should always be installed with the cable gland facing downwards or to the side. For side mounting, it is recommended to lay the connection cable in a drip loop so that water can drain off safely. Electrical connection is easy via the easily accessible screw terminals inside the housing.
Performance and service life: What influences sensor quality?
The quality and longevity of an absolute pressure transmitter are significantly influenced by the environmental conditions and the electrical installation. Although the robust IP65 housing reliably protects the sensor from dust and moisture, extreme temperatures can impair measurement accuracy. A stable and correct power supply is equally important to avoid fluctuations in the measured values. Our transmitters are tested for electromagnetic compatibility (EMC) to ensure that they operate without interference even in the vicinity of other electrical components and to guarantee long-term precision.
What should you look for when choosing an absolute pressure transmitter?
When selecting the right absolute pressure transmitter, several criteria are crucial to ensure optimal function in your application. First, check the required accuracy and temperature influence, because depending on the application, whether simple monitoring or precise control, different levels of stability are required. A key advantage of our transmitters is their flexibility in terms of output signal and measuring range. Ensure that the selectable options (0-10 V or 4-20 mA) and the available pressure ranges are compatible with your control system. Also decide whether you need a local display for quick on-site checking and select the version with or without a display accordingly.
Where can I find all the technical data for the absolute pressure transmitters?
All detailed technical information about our absolute pressure transmitters can be found directly on the respective product pages in our online shop. The complete data sheets and operating instructions are available for download there. These documents contain all the relevant specifications on measuring ranges, accuracy, electrical connection, and environmental conditions that you need for planning and integration.
Frequently asked questions about absolute transmitters?
What is the difference between absolute pressure and relative pressure?
Absolute pressure is always measured relative to a perfect vacuum (0 bar) and is therefore independent of the environment. Relative pressure measures the pressure in relation to the current prevailing, fluctuating atmospheric air pressure.
Why is the transmitter also called a barometer?
A barometer is a measuring device for atmospheric air pressure. Since our absolute pressure transmitter measures precisely this physical quantity, it fulfills the function of a precise, technical barometer for automated systems.
Do I need the version with or without a display?
The version without a display is ideal if the measured value is only processed in a central control system. The version with a display is recommended if you want to read the current pressure value directly on site for quick checking or diagnosis.
How do I set the measuring range and the output signal?
Both parameters can be easily set using DIP switches inside the device. This allows you to flexibly choose between 0-10 V and 4-20 mA as well as one of four measuring ranges without the need for software.
What does the IP65 protection class mean?
IP65 means that the housing is completely dustproof and protected against water jets from all directions. This ensures reliable operation even in demanding environments.
Does the transmitter need to be calibrated?
Our transmitters are factory calibrated and are stable over the long term. For applications that require verifiable accuracy, such as in certified weather measurement technology, regular recalibration is recommended.
Can an absolute pressure transmitter display negative values?
No, this is physically impossible. Since absolute pressure is always measured relative to absolute zero (vacuum), the lowest possible value is 0 bar. Negative values can only occur in relative pressure measurement when a negative pressure (vacuum) is measured in comparison to the ambient pressure.
For which applications is absolute pressure better than relative pressure?
Absolute pressure measurement is always superior when the true pressure must be recorded independently of external influences such as weather or altitude. This is crucial in vacuum measurement, research, or high-precision meteorological applications where fluctuating air pressure must not distort the measurement.
What is the difference between a pressure transmitter and a pressure sensor?
A pressure sensor is the pure measuring element that converts the physical pressure into a usable electrical signal. A pressure transmitter (or transducer) is the complete assembly that contains the sensor and additionally amplifies and linearizes its signal and converts it into a standardized output signal such as 0-10 V or 4-20 mA, which can be transmitted over long distances without interference.
