Internally, electrically heated electrochemical sensing element

US4219399A · kind A · utility

Assignee

• Robert Bosch GmbH · DE

Inventors

• Heiko Gruner · Stuttgart, DE
• Franz Rieger · Aalen, DE
• Rainer Schussler · Bietigheim-Bissingen, DE

Key dates

• Filing date: Sep 10, 1979
• Grant date: Aug 26, 1980
• Expiry date: Sep 10, 1999

Classification

• Technology area (CPC G): Physics
• CPC primary: G01N27/4067
• WIPO field: Measurement
• WIPO sector: Instruments

Abstract

To provide a pre-heated sensor which is capable of heating the sensing element exposed to gases to a temperature of above 400.degree. C. and preferably above 500.degree. C., at which temperature the sensor will be essentially immune to lead content in the gases, an elongated heating rod is placed within a sensor structure in which a solid electrolyte tube is held in position by a first stressed compression spring, the heating rod being formed with a radially projecting flange against which a second compression spring bears, concentrically located within the first, the heating rod itself comprising a long ceramic tube, preferably formed with two longitudinal bores to accept connecting wires to a thermocouple positioned at the end of the tube to sense the temperature of the sensing tube, surrounded by a first metallic tube forming an electrical connection to one terminal of a spiral heating wire which is wrapped around a fiberglass sleeve slipped over the metallic tube, connected to a second metallic tube outside of the fiberglass sleeve which, in turn, has yet another fiberglass sleeve slipped thereover, which is split in the region of the flange, to provide a sensing element in whi…