In order to select the appropriate pressure sensor for an application, you’ll need to consider the purpose of the measurement you’re making. If the measurement should not be influenced by local atmospheric pressure changes, you most probably need an absolute pressure sensor. When the application is using air pressure sensor to determine elevation, such as in an altimeter, an absolute pressure sensor is needed. These sensors are also used in weather stations to measure atmospheric pressure changes.
Sometimes only a small pressure or partial vacuum is all that’s required. This is often the case in medical applications, where partial vacuums are used to remove fluid from wounds. In such situations, the amount of vacuum or pressure needs to be generated with reference to the local atmospheric pressure. This is where the gauge pressure sensor would find a home.
Gauge pressure sensors are also used in industrial applications to determine the fill level of open tanks. The level of liquid can be calculated using the hydrostatic method, which leverages knowledge of the liquid’s specific gravity. If the exact pressure measurement is of less importance, and you only need to determine the pressure difference between two points in the system, a differential pressure sensor is required.
Many systems, such as HVAC, employ filters to clean the air passing through their ducts. You could use a pressure sensor here to determine whether or not the filter needs replacement. The sensor would measure the air pressure both before and after the filter. Once the pressure difference rises above a predefined threshold, it is time to replace the filter. (See diagram below)