Capacitive differential pressure sensor

• US 20040105215A1
• Filed: 10/06/2003
• Published: 06/03/2004
• Est. Priority Date: 04/05/2001
• Status: Active Grant

• Current Assignee: Endress + Hauser GmbH + Company KG (Endress+Hauser AG)
• Original Assignee: Endress + Hauser GmbH + Company KG (Endress+Hauser AG)
• Inventors: Hegner, Frank, Rossberg, Andreas, Drewes, Ulfert, Schmidt, Elke
• Granted Patent: US 6,925,884 B2
• Time in Patent Office: Days
• US Class Current: 361/328
• CPC Class Codes: G01L 13/025 using diaphragms
• CPC Class Codes: G01L 9/0073 using a semiconductive diaphragm
• CPC Class Codes: G01L 9/0075 using a ceramic diaphragm, e.g. alumina, fused quartz, glass

Abstract

In a differential pressure sensor, the measurement value is corrected with the help of the nominal pressure NP. In this way, influences on the measurement value because of deformations of the body of the differential pressure sensor and change in the material stiffness of the membrane are decreased.

Claims

1. Differential pressure sensor comprising

a first ceramic body (20a) with a first membrane bed (22a),

a second ceramic body (20b) with a second membrane bed (22b),

a membrane (30), which is arranged between the two bodies (20a,20b) and separates the two oppositely situated membrane beds (22a, 22b) from one another,

a first measurement capacitor K1 for producing a first measurement signal S1 with a first electrode pair (40a, 40b), which is present as one electrode on the membrane bed (22a) and one electrode on the membrane (30),

a second measurement capacitor K2 for producing a second measurement signal S2 with a second electrode pair (41a, 41b), which is present as one electrode on the membrane bed (22b) and one electrode on the membrane (30),

an electronic circuit

which determines from the two measurement signals S1 and S2 the capacitances CK1, CK2 of the two measurement capacitors K1, K2,

which produces a signal SIG1=1/CK1−

1/CK2, which is essentially proportional to the value of the pressure difference DP and which depends on the nominal pressure NP,

which produces a signal SIG2=1/CK1+1/CK2, which is proportional to the value of the nominal pressure NP,

wherein the dependence of the measurement value DP on the nominal pressure NP is corrected with the help of the signal SIG2.

2. Differential pressure sensor as claimed in claim 1, characterized in that the nominal pressure NP is determined from a polynomial expression.

3. Differential pressure sensor as claimed in claim 2, characterized in that the polynomial expression has the form NP=C0+C1*SIG1+C2*SIG1²+C3*SIG2.

4. Differential pressure sensor as claimed in claim 3, characterized in that the pressure difference DP is determined from the equation DP=C4+C5*SIG1+C6*SIG1*NP+C7*NP.

5. Differential pressure sensor as claimed in one of the preceding claims, characterized in that it is of ceramic.