Pressure sensor

• US 6,363,790 B1
• Filed: 10/15/1999
• Issued: 04/02/2002
• Est. Priority Date: 10/23/1998
• Status: Expired due to Term

• Current Assignee: Endress+Hauser GmbH+Co (ENDRESS)
• Original Assignee: Endress+Hauser GmbH+Co (ENDRESS)
• Inventors: Uehlin, Thomas, Flögel, Karl
• Primary Examiner(s): Fuller, Benjamin R.
• Assistant Examiner(s): AW MUSSE, ABDULLAHI H
• Application Number:
  US09/418,927
• Time in Patent Office: 900 Days
• Field of Search: 737/08, 737/16, 737/17, 737/18, 737/19, 737/20, 737/21, 737/22, 737/15, 737/56, 361/283.4
• US Class Current: 73/708
• CPC Class Codes: G01L 19/04 Means for compensating for effects of changes of temperature , i.e. other than electric compensation
• CPC Class Codes: G01L 9/0075 using a ceramic diaphragm, e.g. alumina, fused quartz, glass

Abstract

The invention is concerned with a pressure sensor which avoids temperature hysteresis effects caused on account of heat-induced expansions as a result of stresses between a ceramic pressure-measuring cell and a metallic housing.

The inventive pressure sensor (100) for determining the pressure of a process medium comprises a metallic housing (110), which is open to a process medium and has a continuous hole (111) for accommodating the ceramic pressure-measuring cell (120), the pressure-measuring cell (120) comprising a ceramic base body (122) and a ceramic diaphragm (121), which is fitted thereon and is exposed to the process medium, and also suitable means (124a, 124b, 130), which supply an electrical signal which can be picked off and corresponds to the process pressure acting on the diaphragm (121). The pressure-measuring cell (120) is fixed axially in a resilient manner in the housing (110) by means of a metallic fixing device (150) which acts on a non-metallic intermediate body (140), which is provided between the pressure-measuring cell (120) and the fixing device (150) and can be moved radially at least with respect to the fixing device (150).

Claims

1. A pressure sensor for determining the pressure of a process medium, comprising:

a metallic housing, which is open to the process medium and

which has a continuous hole for accommodating a ceramic pressure-measuring cell, the ceramic pressure-measuring cell including

a ceramic base body and

a ceramic diaphragm, which is fitted thereon and is exposed to the process medium, and

means for supplying an electrical signal which can be picked off, said electrical signal corresponding to flexing caused by the pressure acting on the diaphragm wherein

the diaphragm is resiliently mounted in the housing on a first stop;

the base body is supported on a non-metallic intermediate body, which

is retained by a metallic fixing device in the housing, and

the intermediate body can be moved radially with respect to the metallic fixing device; and

wherein the intermediate body is composed of a material whose thermal expansion coefficient corresponds to that of the ceramic base body of the pressure-measuring cell.

2. The pressure sensor (100) as claimed in claim 1, in which the metallic fixing device (150) is a metallic ring or a disk which is fixed in a releasable manner in the housing (110).

4. The pressure sensor as claimed in claim 1, in which the intermediate body is composed of ceramic material.

5. The pressure sensor as claimed in claim 1, in which the intermediate body has a centering part, which at least partially encompasses the pressure-measuring cell radially for the purpose of centering the pressure-measuring cell and the intermediate body in the housing.

7. The pressure sensor as claimed in claim 1, in which cutouts are provided in a first end face of the intermediate body, said first end face resting on the pressure-measuring cell, through which cutouts electrically conductive connections are routed.

9. The pressure sensor as claimed in claim 1, in which a film made of cold-flowing material is arranged between the intermediate body and the fixing device.

3. A pressure sensor for determining the pressure of a process medium, comprising:

a metallic housing, which is open to the process medium and

which has a continuous hole for accommodating a ceramic pressure-measuring cell, the ceramic pressure-measuring cell including

a ceramic base body and

a ceramic diaphragm, which is fitted thereon and is exposed to the process medium, and

means for supplying an electrical signal which can be picked off, said electrical signal corresponding to flexing caused by the pressure acting on the diaphragm wherein

the diaphragm is retained axially and resiliently in the housing by a process connection;

the base body is supported on a non-metallic intermediate body, which

is retained by a metallic fixing device in the housing, and

the intermediate body can be moved radially with respect to the fixing device; and

wherein the intermediate body is composed of a material whose thermal expansion coefficient corresponds to that of the ceramic base body of the pressure-measuring cell.

6. The pressure sensor as claimed in claim 3, in which the intermediate body has a centering part, which at least partially encompasses the pressure-measuring cell radially for the purpose of centering the pressure-measuring cell and the intermediate body in the housing.

8. The pressure sensor as claimed in claim 3, in which cutouts are provided in a first end face of the intermediate body, said first end face resting on the pressure-measuring cell, through which cutouts electrically conductive connections are routed.

10. The pressure sensor as claimed in claim 3, in which a film made of cold-flowing material is arranged between the intermediate body and the fixing device.

11. The pressure sensor as claimed in claim 3, in which the intermediate body is composed of a ceramic material.