Pressure sensors – Size

Dimensions: criteria for selecting pressure sensors

The size of a pressure sensor or pressure transducer plays a crucial role and can be derived from the requirements of the specific application. The following guide serves to determine the correct size based on technical parameters and application examples. Generally, it should be considered that small pressure sensors are usually more complex to manufacture and therefore more expensive than larger models.

Pressure range

Depending on the application, the pressure range in which the sensor must operate can vary. This influences the choice of size. A sensor for high pressures can often be more compact than one for low pressures. For example, applications in ventilation and air conditioning systems often require sensors with a low-pressure range, while hydraulic systems need sensors with a much higher pressure range.

Space availability

The available space in the application must be measured in advance to ensure that the selected sensor or transmitter fits into the available space without leading to difficult installation. Additionally, the pressure sensor must be accessible for calibration or easy and quick replacement in case of damage. Pressure sensors for liquid media should be mounted with the pressure connection facing upwards, and sensors for measuring air and gases should be mounted with the pressure connection facing downwards.

Environment

The environmental conditions in which the sensor will operate must always be considered. This includes factors such as temperature, humidity, chemical influences, and potential mechanical stresses such as shock and vibration. A sensor used outdoors or in an environment with extreme temperatures may need to be robustly constructed to withstand these conditions.

Accuracy requirements

The accuracy requirements vary depending on the application. In some cases, very precise measurements are required, while in other applications, a rough estimate of pressure is sufficient. The size of the sensor can affect accuracy, as larger sensors often allow for more precise measurements.

Mounting options

Some applications require special mounting brackets or methods, which can influence the choice of size. To measure fast, dynamic pressure changes of, for example, 1 to 10 milliseconds, the pressure sensor must be installed as close as possible to the medium. This often requires a small form factor. This is typical for pressure profiles at pumps or solenoid valves. For slow, static pressure changes, larger form factor pressure sensors can be used. A mounting location is chosen with sufficient space and moderate environmental conditions. The process connection, from the pressure sensor to the plant, is made via a hose or a pipeline. This allows the use of more cost-effective pressure sensors. A typical application is filter monitoring. A differential pressure sensor is mounted at a location with moderate environmental conditions and connected to the filter via hoses or pipelines.

Example applications in pressure measurement

Pressure sensors in vehicle testing

In the development of hydraulic brake systems, miniature sensors are needed to measure the dispensability and consistency of brake pressure. The pressure change in the brake system is extremely dynamic. Therefore, the measurement must be carried out as close as possible to the brake caliper, where adverse conditions prevail. High temperatures, shock, and vibration require miniaturized pressure sensors that are designed for such environmental conditions. The measurement range of brake pressure is around 200 bar, with a required burst pressure exceeding 400 bar, ensuring the brake line remains pressure-resistant under any stress.

Ventilation and air conditioning systems (HVAC)

Balanced room pressure is crucial for preventing air flows between individual rooms and rooms to the ambient air outside buildings. Room pressure sensors are used in clean rooms, laboratories or operating theatres where precise control of air pressure is required.

Differential pressure sensors are used in HVAC systems to measure the pressure difference between two points. This can be, for example, the difference between the air pressure before and after an air filter to monitor the contamination of the filter. In both applications, the typical pressures are only a few pascals. Accordingly, the pressure sensors must be relatively large in order to be able to detect the small pressure changes. There is usually enough space available so that the sensors can be mounted in a suitable location and connected via hoses