Gauge – Gauge pressure refers to pressure measurements in relation to atmospheric pressure. A gauge pressure sensor has either a vent hole or vent tube that allows the back side of the sensors diaphragm (internal to the sensors housing) to see the same atmospheric pressure as the pressure port side of the diaphragm. This is why gauge sensors read zero pressure when the port is open to atmospheric pressure. Gauge pressure reference is commonly used in low pressure applications as changes in barometric pressure from weather or altitude changes can have a considerable effect on the output of the sensor (manifested as zero shift).
Sealed Gauge – Sealed gauge refers to a sensor that has atmospheric pressure sealed on the inside (backside) of the sensor’s housing. There are no vent holes or vent tubes to the outside. The atmospheric pressure sealed inside the sensor is determined at the time of housing closure (usually by welding). Sealed gauge reference is common in high pressure applications where changes in atmospheric pressure have a negligible effect on the output of the sensor. Customers may also consider a sealed gauge reference in applications where a lot of moisture or submergence may occur.
Absolute – Absolute pressure refers to pressure measurements in relation to a full vacuum. For example, if an absolute pressure sensor is held open to the air then the sensor will read the actual barometric pressure at that location. Therefore, absolute pressure sensors are also affected by altitude changes and other barometric changes.