The differential pressure transducer dpt is used in plethysmograph setups for studying pulmonary function.

The dpt transducer measures the pressure difference between the chamber containing the subject and either a reference chamber or the atmosphere.

The pressure difference varies with the subject's breathing, and is determined by thorax movement associated with breathing, and also, for certain setups, air flow into and out of the subject's body associated with this breathing. 

The dpt transducer is connected to a strain-gauge amplifier.