DIFFERENTIAL PRESSURE MEASURING INSTRUMENT

PURPOSE: To prevent measurement accuracy for decreasing, which may be generated in the case when the pressure of one side of a measurement differential pressure is extremely high. CONSTITUTION: A septum unit 27 and a sub-body 25 are inserted into spot facing parts with small diameter and large diameter of the spot facing hole of a body so that a constant clearance of approximately 2-3mm is available between each left end face and right end face. An extremely hard belleville spring 10 with an extremely large spring constant is inserted into a clearance which is planned in terms of design so that the clearance can be buried. The beleville spring 10 is manufactured by curving and deforming an annular (ring- shaped) flat plate consisting of a spring material, thus preventing the sub-body 25 from being further deformed when it is subjected to an extremely high one- sided pressure. The deformation prevention means prevents the deformation from remaining when the one-sided pressure disappears and the essential inner volume for enclosing liquid from changing, and hence a delicate zero-point fluctuation and further reduction in measurement accuracy are prevented.