Pressure sensor

• US 20040149042A1
• Filed: 01/23/2004
• Published: 08/05/2004
• Est. Priority Date: 02/22/2000
• Status: Active Grant

• Current Assignee: Endress+Hauser GmbH+Co (ENDRESS)
• Original Assignee: Endress+Hauser GmbH+Co (ENDRESS)
• Inventors: Flogel, Karl, Uehlin, Thomas, Hegner, Frank, Drewes, Ulfert, Martin, Rainer, Schmidt, Elke, Banholzer, Karlheinz, Gerst, Peter
• Granted Patent: US 6,848,318 B2
• Time in Patent Office: Days
• US Class Current: 73/723
• CPC Class Codes: G01L 9/0075 using a ceramic diaphragm, e.g. alumina, fused quartz, glass

Abstract

A pressure sensor that is particularly suitable inter alia for the food industry and the measuring accuracy of which is stable over a long time, having a diaphragm seal (3, 45) with a separating diaphragm (7, 53) on which a pressure (P) to be measured acts and having a ceramic measuring cell (9, 57) which is connected to the diaphragm seal (3, 45) exclusively by inorganic materials, is provided, in which sensor the separating diaphragm (7, 53) and all further sensor components coming into contact during measurement with a medium of which the pressure (P) is to be measured are metallic.

Claims

1. A pressure sensor having

a diaphragm seal (3, 45) with a separating diaphragm (7, 53),

on which a pressure (P) to be measured acts, and

a ceramic measuring cell (9, 57) , connected exclusively by inorganic materials to the diaphragm seal (3, 45),

in which the separating diaphragm (7, 53) and all further sensor components coming into contact during measurement with a medium of which the pressure (P) is to be measured are metallic.

2. The pressure sensor as claimed in claim 1, in which the measuring cell (9) is fixed without restraint in a housing (1) by being seated in the axial direction on a small tube (11), via which the ceramic measuring cell (9) is connected to the diaphragm seal (3).

3. The pressure sensor as claimed in claim 1 or 2,

in which the measuring cell (9) has a measuring diaphragm (15),

which subdivides an internal space of the measuring cell (9) into a first chamber (17) and a second chamber (19),

in which the first chamber (17) is connected to the diaphragm seal (3) via a small tube (11),

in which the first chamber (17), the small tube (11) and the diaphragm seal (11) are filled with a fluid,

in which the fluid transfers a pressure (P) acting on the separating diaphragm (7) to the measuring diaphragm (15),

in which a reference pressure acts on the measuring diaphragm (15) in the second chamber (19), and

which has an electromechanical transducer for registering a deflection of the measuring diaphragm dependent or the pressure (P) and the reference pressure and for converting said deflection into an electrical output signal.

4. The pressure sensor as claimed in claim 3, in which

the reference pressure (P_R) is a reference pressure prevailing in the ambience and the second chamber (19) has an opening (21) through which the reference pressure is introduced into the second chamber (19), or

the second chamber (3) is hermetically sealed and the reference pressure (P_A) is an absolute pressure prevailing in the second chamber (19).

5. The pressure sensor as claimed in one of the preceding claims, in which the measuring cell (9) is additionally enclosed in the radial direction in a holder.

6. The pressure sensor as claimed in claim 5, in which the holder has a body (35) made of an elastomer filling an intermediate space between the measuring cell (9) and the housing (1).

7. The pressure sensor as claimed in claim 1, in which the ceramic measuring cell (57) is fastened by means of a metallic joint (71) in a housing (47) connected to the diaphragm seal (45).

8. The pressure sensor as claimed in claim 5, in which the housing (47) consists of a material which has a coefficient of thermal expansion which is approximately equal to the coefficient of thermal expansion of the ceramic of the measuring cell.

9. The pressure sensor as claimed in claim 1, in which the measuring cell (57) is fastened in an insert (83) which is arranged in a housing (81), is connected to the diaphragm seal (45) and reaches around the measuring cell (57) in a pot-like manner.

10. The pressure sensor as claimed in claim 1, in which the measuring cell is mounted without restraint and isostatically in a chamber which is connected to the diaphragm seal and filled with a fluid, surrounded on all sides by the fluid.