Overload safe pressure sensor, especially pressure difference sensor

Patent metadata

Field	Value
Publication number	US-10101231-B2
Application number	US-201013516423-A
Country	US
Kind code	B2
Filing date	Nov 11, 2010
Priority date	Dec 22, 2009
Publication date	Oct 16, 2018
Grant date	Oct 16, 2018

Abstract

A pressure sensor includes a sensor body with a sensor chamber in the interior, at least a first separating membrane, forming a first separating membrane chamber connected with the sensor body. A measuring membrane divides the sensor chamber into two chamber portions. A pressure transfer liquid, with which the first separating membrane chamber, the first chamber portion and a channel therebetween are filled, in order to transfer a pressure to the measuring membrane; wherein the pressure sensor is specified for a temperature range between a minimum temperature and a maximum temperature, as well as for a pressure range. At the minimum temperature, the pressure transfer liquid volume in the first chamber portion, the first channel and the first separating membrane chamber is sufficient over the total pressure range to transfer the pressure to the measuring membrane, without the first separating membrane coming to rest, and that when, in the case of overload at maximum temperature, the entire pressure transfer liquid volume moves out of the first separating membrane chamber into the first chamber portion, and is accommodated by the measuring membrane, the measuring membrane experiences no plastic deformation.

First claim

The invention claimed is:

1. A pressure sensor, comprising:
a sensor body with a sensor chamber in an interior of the sensor body;
at least a first separating membrane, which, forms a first separating membrane chamber, is connected with said sensor body; and
a measuring membrane, which divides said sensor chamber into two chamber portions;
a pressure transfer liquid, with which said first separating membrane chamber, said first chamber portion and a channel therebetween are filled, in order to transfer a pressure to said measuring membrane; wherein:
the pressure sensor is specified for a temperature range between a minimum temperature and a maximum temperature, as well as for a pressure range;
at the minimum temperature, a pressure transfer liquid volume in said first chamber portion, said first channel and said first separating membrane chamber is sufficient over the total pressure range to transfer the pressure to said measuring membrane, without said first separating membrane coming to rest; and
when, in the case of overload at the maximum temperature, an entire pressure transfer liquid volume moves out of said first separating membrane chamber into said first chamber portion and is accommodated by said measuring membrane, said measuring membrane experiences no plastic deformation;
wherein

V

m
⁢

⁢
ax

≤

R
4

h

·

π
12

·

(

1
-

υ
2

)

·

1
S

⁢

σ

ma
⁢

⁢
x

E

,

with a safety factor S≥1, wherein Vmax is a maximum volume of the pressure transfer liquid in the separating membrane chamber in the resting position of the pressure sensor, wherein R and h are radius and thickness of the measuring membrane, respectively, wherein v is Poisson's ratio of material of the measuring membrane, wherein smax is a maximum allowable stress of the material of the measuring membrane, and wherein E is a modulus of elasticity of the material of the measuring membrane, wherein:

V

m
⁢

⁢
i
⁢

⁢
n

≥

R
6

h
3

·

π
·

(

1
-

υ
2

)

16
·
E

·

p

m
⁢

⁢
a
⁢

⁢
x

wherein V min is a minimum volume of the pressure transfer liquid in the separating membrane chamber in a resting position of the pressure sensor, and wherein p max is an upper limit of the specified measuring range;
wherein V max =V(T max ), wherein T max is the specified maximum temperature;
wherein V min =V(T min ), wherein T min is the specified minimum temperature;
wherein at the upper limit of the specified measuring range p max , a maximum stress in the measuring membrane amounts to not less than 20% of a maximum allowable stress σ max ;
wherein a difference between the specified maximum temperature and the specified minimum temperature amounts to not less than 125 K;
wherein said measuring membrane comprises a circular disk, which is essentially planar in the resting position; and
wherein said measuring membrane and said sensor body comprise steel.

2. The pressure sensor as claimed in claim 1 , wherein:
said measuring membrane comprises a first material and said sensor body a second material; and
a coefficient of thermal expansion α 1 of said first material deviates by no more than 10% from a coefficient of thermal expansion α 2 of said second material.

3. The pressure sensor as claimed in claim 1 , wherein:
said measuring membrane and said sensor body comprise stainless steel or spring steel.

4. The pressure sensor as claimed in claim 1 , wherein:
said measuring membrane includes at least one measuring-electrode of a capacitive transducer;
said capacitive transducer furthermore has at least one counterelectrode, which is positioned essentially pressure-independently with respect to said sensor body relative to said measuring membrane.

5. The pressure sensor as claimed in claim 4 , further comprising:
a housing; and
at least one electrode support, wherein:
said at least one electrode support comprises a same material as said housing; and said counterelectrode electrically is electrically insulated relative to said measuring electrode.

6. The pressure sensor as claimed in claim 4 , wherein:
said counterelectrode is arranged, spaced from conductive surfaces, in such a manner, that capacitances between said at least one measuring-electrode of said measuring membrane and said counterelectrode amounts to not less than stray capacitance between the electrodes of the capacitive transducer and said sensor body.

7. The pressure sensor as claimed in claim 1 , wherein:
said chamber portion contains a filling element.

8. The pressure sensor as claimed in claim 7 , wherein:
in each case,

Assignees

• Tham Anh Tuan
• Teipen Rafael
• Philipps Michael
• Endress Hauser Se Co Kg

Inventors

• Tham Anh Tuan
• Teipen Rafael
• Philipps Michael

Classifications

• G01L19/04

  Means for compensating for effects of changes of temperature {, i.e. other than electric compensation} · CPC title

• G01L13/025 Primary

  using diaphragms · CPC title

• G01L9/0044

  Constructional details of non-semiconductive diaphragms · CPC title

• G01L19/0618

  Overload protection · CPC title