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1. (WO1998013688) DIAGNOSTIC METHOD AND APPARATUS FOR SOLID ELECTROLYTE GAS ANALYZER

Pub. No.:    WO/1998/013688    International Application No.:    PCT/US1997/016002
Publication Date: Apr 2, 1998 International Filing Date: Sep 10, 1997
IPC: G01N 27/406
G01N 27/417
Applicants: ROSEMOUNT ANALYTICAL INC.
Inventors: FARBER, Boris, Y.
O'NEILL, Michael, G.
ESTVANDER, Michael, T.
THOMSON, James, W.
Title: DIAGNOSTIC METHOD AND APPARATUS FOR SOLID ELECTROLYTE GAS ANALYZER
Abstract:
A solid electrolyte gas analyzer (40) is equipped with a diagnostic circuit (50) that intermittently measures an impedance of the solid electrolyte measurement cell (60) as an indication that the cell is in need of calibration or replacement. The disgnostic operation is performed on the cell (60) in situ, i.e., while the solid electrolyte cell (60) is exposed to the gas to be measured and heated to a controlled elevated temperature. Preferably the cell impedance is measured at a predetermined frequency by injecting a modulated current through the cell (60) and measuring the resulting voltage drop.