Unidirectional Differential Pressure Sensor

Unidirectional pressure transducers measure between zero and a positive pressure. Unidirectional differential pressure sensors contain a diaphragm that will only deflect in a single direction. Higher pressure has to be applied to the pressure port defined as "high pressure". If you accidentally spec a unidirectional sensor for an application that requires both positive and negative differential pressure, you will most likely damage your sensor.

These kinds of transducers are used in applications where the direction of flow is known and is not expected to change. If the flow of air reverses, the transducer will be out of range of what it can monitor.