Part 1 provided background on the evolution of heating, ventilation and air-conditioning (HVAC) systems and the increased use of sensors in these systems. Today, sensors are used both to monitor the indoor environment as well as to monitor and control the equipment that is used to cool or heat, humidify or dehumidify as well as to monitor the indoor air quality in HVAC systems. Sensors for these applications including pressure, temperature, humidity, vibration and others.
Today’s more advanced HVAC designs include variable air volume (VAV), energy recovery ventilation (ERV) and filter blockage applications. In advanced systems, the amount of control that HVAC designers put into their systems has a lot to do with what they can sense. This includes aspects including temperature, air flow, air direction, air speed and several aspects specifically in the motors. For example, in commercial building applications air flow is very important.
“When they are sizing a building, the types of airflow that the building has becomes critical,” says Paul Sittard, Account Manager, Sensors Group at TE Connectivity. “A VAV system on the low end is sized for 0.3” of water and we can detect pressures way below that.”
For example, TE Connectivity’s LDE/LME/LMI differential pressure sensors measure ultra-low air or gas pressures from 25 Pa (0.1” H2O) full scale. The sensors are based on thermal flow measurement of gas through a micro-flow channel integrated within the sensor chip.
The LHD ULTRA differential low-pressure sensors for VAV and other applications use dual micro-flow channels to effectively maximize the dynamic range of the sensor. Pressure ranges from 1250 to 5000 Pa (5 to 20” H2O) with resolution of ~0.05 Pa (0.0002” H2O) at low pressure. These are printed circuit board mounted sensors that can be used in residential or commercial applications.
Part 3 will discuss ongoing changes to today’s HVAC systems and the impact on sensors.
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