Pressure sensors, transducers and transmitters are stationary pressure gauges designed to continuously monitor atmospheric pressure, gas pressure, or differential pressure by comparing two simultaneous pressure measurements. Very often in the field of ventilation, the pressure measurement of manometers is exploited to measure the flow rate and velocity of an air stream, using a Pitot tube or a DEBIMO wing. 

Some pressure sensors are designed to automatically control the activation or deactivation of a system to which it is connected according to a given pressure value. They are called pressure switches or manostats, which act in a similar way to a thermostat for temperature. 

Many of today's manometers are electronic and digital, based on piezoelectric sensor technology. But to be independent of any power source, and to operate under any circumstances, some installations require a liquid column model of pressure gauge instead. 

Essential in ventilation systems 

Ventilation and air-conditioning systems in buildings require pressure transmitters at various locations to monitor their correct operation and to optimise their performance in order to reduce energy consumption. These sensors are usually placed at strategic points in the ventilation system: 

  • At the filters of the air handling unit (AHU): a differential pressure transmitter will compare the pressure before and after the air filters. If the pressure before the filters is too high compared to the pressure after the filters, it means that the filters are clogged and do not let enough air through, reducing the efficiency of the air handling system. A filter change is then necessary. 
  • At the air handling unit outlet, a pressure sensor equipped with a DEBIMO wing or a Pitot tube is used to measure the speed and flow rate of the air supplied by the air handling unit in order to know the nominal ventilation capacity of the building. 

Required for regulated environments 

Stationary pressure transducers are also essential in sensitive environments such as laboratories, where the atmosphere must be very finely controlled. Clean rooms and other controlled environments often need to set up pressure cascades to keep certain areas at a higher or lower pressure than the outside areas of the room. This requirement prevents contamination between different areas of a laboratory or even a hospital. 

To ensure these atmospheric conditions, a fixed, built-in or external differential pressure transmitter is used to continuously monitor the pressure differential inside and outside a room. These sensors must have a very high measurement resolution and accuracy, as the pressure differences maintained by the air conditioning system are very small in order not to create turbulence and to remain energy efficient. 

To maintain accuracy over a long period of time, some differential pressure sensors are able to automatically auto-zero their measurement system to ensure the accuracy of their differential pressure measurement.