Abstract: A fluid pressure transducer of the null balance type in which a fluid whose pressure is being sensed acts against one face of a diaphragm and a balancing control fluid acts against the opposite face. Control fluid pressure is uniformly distributed against the control face of the diaphragm by a porous element, preferably made of a sintered material. Movement or displacement of the diaphragm opens a sensing element and may be controlled by use of a similar pressure distributing porous element placed on the sensing side. The volume defined between the two porous elements limits maximum diaphragm travel and displacement. Transducers made according to the invention have high sensitivity. The transducers are particularly well adapted for measurement of pore pressure in earth fills or natural geological environments.

Abstract: A transducer for converting fluid pressure into pneumatic pressure for relay to a remote readout station comprises a valve body having a chamber spanned by a diaphragm which divides the chamber into a pore-fluid pressure cavity and a transducer cavity. The pore-fluid pressure cavity is in communication with fluid pressure in the environment surrounding the buried valve body. Three ducts communicate with the transducer cavity. The diaphragm carries a centrally located resilient hemisphere within the transducer cavity in axial alignment with only one of said ducts which constitutes a vent from said transducer cavity.