Method for producing capacitive ceramic absolute pressure sensors sorted in zero-point long-term stability defect classes

US5836063A · kind A · utility

Assignee

• ENVEC Mess- und Regeltechnik GmbH + Co. · DE

Inventors

• Frank Hegner · Bad Kötzting, DE
• Lukas Klausmann · Bocholt, DE

Key dates

• Filing date: Mar 5, 1997
• Grant date: Nov 17, 1998
• Expiry date: Mar 5, 2017

Classification

• Technology area (CPC Y): Emerging Cross-Sectional Technologies
• CPC primary: Y10T29/435
• WIPO field: Measurement
• WIPO sector: Instruments

Abstract

In this method for producing capacitive alumina-ceramic absolute pressure sensors sorted in high-precision zero-point long-term stability defect classes referred to a measured-value span c.sub.sp, the sensors are firstly produced conventionally: a substrate is provided with an annular first electrode and, at the center, a circular second electrode insulated from the first; a diaphragm is provided with a third electrode, and the substrate and diaphragm are joined tightly together in a vacuum by the mutually facing electrodes, at an outer edge through the interposition of an active brazing ring with the formation of a chamber, with the result that a pressure-dependent capacitance C.sub.p and a pressure-independent capacitance C.sub.r are produced. Then, using the equation c=(C.sub.p -C.sub.r)/C.sub.p =k.sub.1 (p-p.sub.0)+k.sub.0, at room temperature and under a vacuum (=p.fwdarw.0) a first zero value c.sub.n1 =-k.sub.1 p.sub.0 +k.sub.0 is determined by means of a capacitance zero-point measuring device having the zero-point measuring error F.sub.n. A second zero value c.sub.n2 =-k.sub.1 p.sub.0 '+k.sub.0 is determined for each sensor by means of the same measuring device after the se…