DM Experts Knowledge “Asked – Known!”
Why are there pressure sensors for different temperature ranges and how do I determine the right temperature range for my application?
Pressure sensors can be used in a variety of temperature ranges, whereby their performance depends on the specific design and the materials used. DDM manufactures pressure sensors, pressure transmitters and pressure transmitters for all typical industrial temperature ranges. DDM has years of experience and the necessary expertise to cover applications from -54°C to +150°C.
Your application – our customised pressure sensors
DDM manufactures pressure transmitters for the standard temperature ranges 0°C to 50°C, -20°C to +80°C, -40 to +125°C and -54°C to +150°C. Within the limits of -54°C and +150°C, any customised temperature range can be produced individually.
Standard Temperature Ranges and Customization
Pressure sensors for different temperature ranges exist for several reasons related to the requirements of different applications and the physical properties of materials. Here are some reasons why there are pressure sensors with different temperature ranges:
Material selection: The components from which pressure sensors are made have specific temperature limits beyond which their performance can be affected. Different applications require different materials that are suitable for the specific temperature ranges.
Accuracy and precision: Pressure sensors must be able to provide accurate and precise measurements. Accuracy can be affected by temperature variations. Sensors designed for a specific temperature range use specific compensation methods to fulfil the accuracy requirements.
Temperature Compensation: Requirements for pressure sensors vary with applications. Some need to measure pressures at extreme temperatures, while others operate in moderate conditions. Sensors are developed and manufactured accordingly.
Temperature compensation for pressure sensors
Temperature compensation in pressure sensors is crucial to ensure accurate readings over a wide temperature range. DDM successfully utilises an active compensation method. A temperature measuring point integrated in the pressure sensor permanently supplies a temperature signal. The pressure sensor is calibrated at different temperatures according to the desired temperature range. The measured values obtained (pressure signal and temperature signal) are implemented in algorithms to correct the measurements in real time. Calibrating a pressure sensor is time-consuming and cost-intensive. For the standard temperature range 0°C to 50°C, the calibration time is around 3 hours and for the range -40 to +125°C up to 24 hours. It is most economical to select the smallest possible temperature range for the individual application.
Decision-making aids for selecting the temperature range
Below we provide some decision-making aids to help you determine the optimum temperature range for your application:
Temperature range 0°C to 50°C – Industry and process technology:
All systems that are installed inside buildings and are not exposed to winter conditions – provided that the medium to be measured is also within this temperature range.
- Heating, ventilation, air conditioning
- Process industry
- Food industry
- Beverage production
- Machines and systems e.g. presses, vacuum packaging systems…
- Medical technology e.g. blood pressure measurement, dialysis…
Temperature range -20°C to 80°C – outdoor area:
All systems that are installed outside buildings and are exposed to both Central European winter conditions and direct sunlight – provided that the medium to be measured is also within this temperature range.
- Barometers in weather stations
- Waste water Sewage treatment plants
- Well level
- Sluice control
- Water supply systems
- Gas supply and storage
- Cooling units
Temperature range for -54°C to 125°C – extreme temperatures and demanding environments:
All systems installed outside buildings and exposed to arctic winter conditions as well as direct sunlight or other heat-emitting sources – provided that the medium to be measured is also within this temperature range.
- all applications listed below -20°C to 80°C that are operated in latitudes with arctic conditions
- Passenger cars and commercial vehicles
- rail vehicles
- military equipment
- aeroplanes
- satellite technology
Example of sterilisation process and pressure sensor
If you look at a pressure sensor, you will see that different temperatures may act on it at the same time. These temperatures are referred to as the process or medium temperature and the ambient temperature. The sterilisation process in a steam-operated autoclave illustrates the effect of different temperatures on a pressure sensor in an easily understandable way. While the ambient temperature corresponds to the local room temperature and remains virtually constant, the process temperature changes constantly.
How it works:
- Vacuum and preheating: The sterilisation process begins with a vacuum to remove the air from the steriliser. This is followed by preheating to bring the instruments or the material to be sterilised to the requested temperature.
- Steam supply: Steam is introduced into the steriliser to fill the sterilisation chamber.
- Pressure and temperature increase: The steam pressure and thus the temperature are increased to create optimum sterilisation conditions.
- Sterilisation phase: The sterilising effect is achieved by the combined effect of steam pressure and high temperature over a defined period of time. Depending on the items to be sterilised, the temperatures are +121°C or +134°C
Role of the pressure sensor: The pressure sensor in a steam-powered steriliser fulfils several important tasks:
- Pressure monitoring: the pressure sensor monitors the steam pressure during the sterilisation process. A constant and predefined pressure is crucial to ensure the effectiveness of sterilisation.
- Regulation and control: The pressure sensor provides feedback on the current pressure to the steriliser’s control system. The system can then regulate the steam inlet and outlet to maintain the desired pressure.
- Safety function: The pressure sensor plays a crucial role in the safety of the steriliser. It detects excessive pressure fluctuations or increases that could indicate malfunctions and, if necessary, triggers protective measures to ensure user safety.
Properties of the pressure sensor: The pressure sensor in a steriliser must have certain properties:
- Accuracy and precision: a high degree of accuracy is required to ensure that the steam pressure in the steriliser is measured accurately while the process temperature varies cyclically between +20°C (filling and evacuation) and +121°C or +134°C (sterilisation phase).
- Temperature resistance: The pressure sensor must be able to withstand temperatures that occur during the sterilisation process.
- Reliability: : The reliability of the pressure sensor is critical to ensure consistent monitoring throughout the sterilisation cycle.
- Fast response time: A fast response time is important so that the pressure sensor can react quickly to changes in vapour pressure.
Specific pressure sensor solution for sterilisation applications
For this application, DDM manufactures a customised pressure sensor whose electronic components are designed to be permanently temperature-resistant for a sterilisation temperature of +134°C. The use of high-quality components guarantees reliable operation and a long service life. The compensated temperature range is individually designed for the working range of the steriliser and extends from +15°C to +140°C. This minimises the calibration time. This minimises the calibration time and achieves the high accuracy required to measure the vapour pressure precisely. All wetted parts are made of stainless steel, welded without seals. The design of the process connection is flush with the front so that no dead spaces are created and the pressure sensor can be sterilised as a SIP system component.
