In air conditioning technology it is vital that airstreams and pressures in rooms and piping are monitored to enable heating, ventilation and air conditioning systems to be operated in an energy-efficient and cost-effective manner. Here, pressure sensors are a central element in regulation.

In order to meet strict statutory requirements and minimize energy costs, sensors with ever smaller measurement ranges and higher measurement sensitivities, accuracies and long-term stability are required. Customer service demands that these must be replaceable. The pressure sensor must also satisfy the special demands of air conditioning technology, such as the processing of dusty air or greasy exhaust air, and be easy to integrate in the minimum of space as an OEM system.

Air conditioning sub-applications:

  • Volume flow measurement
  • Filter monitors
  • Pipe and duct monitoring
  • Room pressure control


Volume flow measurement

Differential low pressure sensors measure the drop in pressure across a flow element, such as an aperture, as a gage of the volume flow. The sensor is located in a bypass of the main flow line. In volume flow controllers for variable air volume (VAV) the pressure measurement controls the flap position within a closed control circuit, thus enabling demand-based ventilation. Ventilation in buildings is important for the control and monitoring of building facilities. Reducing the airstreams in buildings considerably lowers operating costs. Costs are cut by reduced fan outputs and less consumption of energy for air preparation (heating, cooling, humidification and dehumidification) and the system lifetime is lengthened. A variable air/volume flow is essential in buildings today. It must be regulated depending on the air quality, room temperature and room humidity and under consideration of the building’s users.

Filter monitors

Soiled air filters increase the loss of pressure in air ducts and systems, resulting in higher fan outputs and a rise in energy costs. An electronic filter monitoring system with an integrated differential pressure sensor measures the drop in pressure across the filter and triggers a filter change warning in good time. Sensitive pressure sensors thus considerably help to ensure that ventilation and air conditioning systems operate cost effectively. Monitoring differential pressure also allows defects such as torn filters to be detected.

Pipe and duct monitoring 

When ventilation flaps to various rooms are opened and closed, the pressure in the air ducts changes. The ventilating system fan is controlled on demand to ensure a constant pressure in the air duct and achieve efficient ventilation and air conditioning. A pressure sensor monitors the duct pressure and controls the fan output, thus largely contributing to the reliability, safety and economy of the system.

Room pressure control 

In air-conditioned rooms the intake and exhaust air must be controlled so as to minimize the difference in pressure between the individual zones or compared to the immediate surroundings.

In contrast, in clean rooms a constant positive pressure must be ensured to prevent unpurified air from entering the area. In laboratories and hospitals, on the other hand, a constant negative pressure prevents the spread of germs and dangerous substances. In all applications high-precision pressure sensors monitor the very slight differences in pressure between the different areas, thus enabling the necessary safety precautions to be taken.