CAPACITIVE PRESSURE TRANSDUCER

• US 3,697,835 A
• Filed: 05/24/1971
• Issued: 10/10/1972
• Est. Priority Date: 05/25/1970
• Status: Expired due to Term

• Current Assignee: Gyula Satori
• Original Assignee: Gyula Satori
• Inventors: Satori, Gyula
• Primary Examiner(s): Goldberg, E. A.
• Application Number:
  US05/145,087
• Time in Patent Office: 505 Days
• Field of Search: 317/246,24R,250 179/106 73/398C
• US Class Current: 361/283.4
• CPC Class Codes: G01L 13/025 using diaphragms
• CPC Class Codes: G01L 9/0072 using variations in capacitance

Abstract

Known capacitive pressure transducers comprise a wheatstone bridge connection in each branch of which there is a capacitance. Two of them are variable while the two others are arranged on a diaphragm in a casing. The chamber of the casing is subdivided by the diaphragm into a pair of compartments and each compartment is arranged for being connected to a system the pressure of which is to be measured. Such arrangement requires considerable space and is intricate to manipulate. Moreover, its output signals are of low level due to only one pair of capacitances being variable. This invention employs four variable capacitances distributed in the individual branches of a Wheatstone bridge connection for which purpose four electrodes are supported on opposite sides of the diaphragm. Further four electrodes are arranged within the casing opposite to the electrodes on the diaphragm. Thus, four variable capacitances are formed which are connected to form a wheatstone bridge connection. Deflections of the diaphragms caused by such pressure entail variations of the bridge capacitances and, thereby output voltage signals of increased strength on the bridge terminals.

Claims

1. A capacitive pressure transducer comprising, in combination, a casing (12), a diaphragm (10) in said casing and subdividing its interior into a first pressure compartment (62) and a second pressure compartment (64), a first terminal (54), a second terminal (56), a third terminal (58) and a fourth terminal (60) in the wall of said casing (12), a first capacitive electrode (24) and a second capacitive electrode (26) on the wall of said casing confining said first pressure compartment (62), a third capacitive electrode (25) and a fourth capacitive electrode (27) on the wall of said casing confining said second pressure compartment (64), a fifth capacitive electrode (36) and a sixth capacitive electrode (38) on one side of said diaphragm facing said confining wall of said first pressure compartment (62), a seventh capacitive electrode (32) and an eighth capacitive electrode (34) on the opposite side of said diaphragm facing said confining wall of said second pressure compartment (64), a first contact streak (54a) connecting said first terminal (54) by a first connection lug (26a) with said second capacitive electrode (26) and by a second connection lug (25a) with said third capacitive electrode (25), a second contact streak (50) connecting said third terminal (58) by a third connection lug (29) with said seventh capacitive electrode (32) and by a fourth connection lug (28) with said fifth capacitive electrode (36), a third contact streak (56a) connecting said second terminal (56) by a fifth connection lug (24a) with said first capacitive electrode (24) and by a sixth connection lug (27a) with said fourth capacitive electrode (27), and a fourth contact streak (52) connecting said fourth terminal (60) by a seventh connection lug (31) with said eighth capacitive electrode and by an eighth connection lug (30) with said sixth capacitive electrode.

2. A capacitive pressure transducer as claimed in claim 1, said casing and diaphragm being circular, a pair of rings that clamp the periphery of said diaphragm between them, and means urging said O-rings radially outwardly entirely about the axis of said casing thereby radially to tighten said diaphragm.