Fuji Electric Co., Ltd.

Mitsuru Tamai

Takeshi Yasuhara

Tadanori Yuhara

Teizo Takahama

Kimihiro Nakamura

Mikihiko Matsuda

Hironobu Yao

Toshiyuki Takano

Masao Saitoh

Isamu Asano

Seiji Suzuki

Etsuro Ito

Kazuaki Kitamura

Shinichi Souma

Masahiro Osakabe

A differential pressure detecting apparatus includes a columnar main body wherein a differential pressure detection portion is inserted into a closed-end hole having a countersunk portion and formed in the outer circumferential surface of said main body at right angles to the axis of the main body, wherein a first seal diaphragm for receiving one of introduced pressures relating to a differential pressure to be measured is provided in one end surface of the main body, and wherein the main body has a hole provided for transmitting the received introduced pressure to the differential pressure detection portion; a disc-like sub-body inserted into the countersunk portion of the closed-end hole, wherein a second seal diaphragm for receiving the other introduced pressure is provided in the outer end surface of the sub-body, and wherein a hole is provided for transmitting the received introduced pressure to the differential pressure detection portion; a cover provided on the one end surface of the main body, and having a hole for the one introduced pressure for the first seal diaphragm; and another cover provided on the outer circumferential surface of the main body, and having a hole for the other introduced pressure for the second seal diaphragm.

Differential pressure detecting apparatus

A pressure measuring apparatus comprising a seal diaphragm that separates a fluid to be measured from a pressure transmitting medium that transmits a pressure variation of the fluid to be measured to a pressure detecting section. In such an apparatus, a non-electrically conductive film is coated on a surface of the seal diaphragm which is on the side of the fluid to be measured. As a result of the above construction, the pressure can be measured accurately over a long period of time while preventing hydrogen from passing through the seal diaphragm surely and protecting the seal diaphragm.

Apparatus for measuring pressure in a fluid using a seal diaphragm and

Pressure measuring apparatus

The present invention is directed to a capacitive differential pressure detector comprising a diaphragm disposed between two electrodes. In a first embodiment, each of the electrodes comprises two conductive plates with an insulator disposed therebetween. Step-like portions are formed in the conductive plate nearest the diaphragm. In a second embodiment, the plate nearest the diaphragm is insulative with a conductive film formed thereon. In a third embodiment, at least one groove is formed in the plate nearest the diaphragm. The groove is formed in a surface of the plate which faces the diaphragm. The groove also intersects a pressure guide hole. In a fourth embodiment, a substrate is disposed on a surface of the plate farthest from said diaphragm. In a fifth embodiment, an insulating layer has the same coefficient of thermal expansion as the conductive plates. In a sixth embodiment, the diaphragm is etched in order to form a circular flexible part, a centrally disposed displacing part, and a bonding part.

Capacitive differential pressure detector

A pressure detector for measuring the pressure of a pressurized fluid by means of electrostatic capacitance comprising a diaphragm displaceable in response to the pressure, and a pair of fixed electrodes, one of each of the fixed electrodes being located on each side of the diaphragm and being electrostatically capacitively coupled to the diaphragm, each of the fixed electrodes being shaped to essentially eliminate electrostatic capacitances that are not differentially linear with respect to the pressure.

Electrostatic capacitance type pressure detector

An electrostatic capacity type pressure detector having a central diaphragm, which is deformed by pressure, and a fixed electrode on each side of the diaphragm. Each of the fixed electrodes includes a first electrically conductive plate confronting the diaphragm, an insulating plate joined to the first conductive plate, and a second electrically conductive plate joined to the first plate. An annular support joined to the diaphragm and to the insulating plate surrounds but is insulated from the first electrically conductive plate. A hole in the electrode introdues pressure into a space defined by the electrode and the diaphragm.

Electrostatic capacity type pressure detector

A pressure sensor the output of which is substantially immune from errors caused by temperature variation or exteriorly applied forces. An insulating disc with metal foil electrodes on the flat surfaces thereof is disposed in an inner cylinder housing between a pressure measuring diaphragm and a reference electrode plate. A first measurement pressure is applied directly to the opposite side of the diaphragm and a second measurement pressure is applied to the side adjacent the insulating disc via a soft rubber diaphragm and an insulating liquid which fills the space between the soft rubber diaphragm and measuring diaphragm extending through apertures in the inner cylinder and insulating disc. The difference pressure is determined by measuring the capacitance difference between capacitors formed by the reference electrode plate and the metal foil layer adjacent thereto and the measuring diaphragm and the metal foil layer adjacent thereto.

Pressure measuring device

A flexible diaphragm-type fluid-filled sensing device is made immune to thermal expansion and contraction errors by providing a constant volume first fluid chamber formed between the insulating block and a metal plate, a second chamber between the metal plate and a sealing diaphragm and a third chamber between the other surface of the block and a measuring diaphragm. The three chambers are connected by fluid passages and the sealing diaphragm is much more flexible than the measuring diaphragm so that any volumetric change in the fluid is followed by the sealing diaphragm without changing the volumes of the first or third chambers to which the electrical displacement sensing devices are attached.

A compact sensing device is provided which the tension applied to the sensing member is substantially uniform and free of thermally changing. Either the sensing member itself or a clamping member disposed around the device or both, are made of a precipitation hardenable metal which will contract during a heat treatment. If the sensing member is thermally contracted a uniform radial tension will result, and if the clamping member is contracted a uniform clamping force applied to the device for tensioning the diaphragm will be provided without the necessity of clamping bolts.

Pressure sensing device

A pressure sensing device is disclosed having the pressure sensing diaphragm positioned in a housing which is not stressed or enlarged by large static pressure. The housing is attached within a recess of a larger casing by means of a support diaphragm. The recesses are communicated with the interior of the housing by passages therethrough to equalize the pressure inside and outside the housing. The outer side of each casing forms a pressure reception chamber with a respective pressure receiving diaphragm. The latter chambers communicate with the recess via passages in the casing. The space between the pressure sensitive diaphragm and each pressure receiving diaphragm, including the housing interior chamber, the housing passage, the casing recess, the casing passage and the pressure receptive chamber, is filled with a fluid. The construction and filling is such that overpressure on one pressure receiving diaphram causes the entire housing to move toward the inner wall of the casing. However the latter diaphragm closes with the outer wall of the casing before the housing contacts the casing inner wall.

Device for use in sensing pressures

A differential pressure measuring cell includes a capacitive-type measuring chamber having a relatively rigid diaphragm, an auxiliary chamber having a relatively flexible diaphragm, a casing defining first and second recesses surrounding the auxiliary and measuring chambers, respectively, passages connecting one side of the auxiliary chamber and measuring chamber with the first recess and a first pressure-receiving chamber, and passages connecting the other side of the auxiliary chamber and measuring chamber with the second recess and a second pressure-receiving chamber. Radial expansion of the auxiliary and measuring chambers is prevented by the static counterpressures present in the first and second recesses. Over pressure protection is provided by the small volumes of the first and second pressure-receiving chambers and the greater flexibility of the auxiliary diaphragm, whereby the auxiliary diaphragm will absorb the entire pressure differential before the measuring diaphragm engages the walls of the measuring chamber.

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Kanagawa, Japan

Mitsuru Tamai