IC engine depressurisation effect measurement - having pressure sensor using change of capacitance effect caused by moving diaphragm

摘要

In the pressure sensor, the capacitance between a moving diaphragm and a base is modified and is used to sense depressurisation effects in an internal combustion engine. The nominal capacitance is determined by having electrode spacing set during manufacture by a sealing ring. A thick cylindrical ceramic base (10) has a lower surface (12) supported on flexible annular spacers (39). Holes (13) around the periphery allow conductors (33,34) to pass through to metallised electrodes (18,22) on the upper surface and on the lower surface of a thin ceramic diaphragm (20). A ring (16) defining an internal cavity (31) is deposited on the base and acts as a sealing support for the diaphragm to define electrode spacing. A hole (37) in the case allows pressure to be applied to the diaphragm.