Determining residual life of electrochemical sensor for e.g. oxygen or pH, extrapolates deterioration in properties over time, until they reach limiting values

摘要

Parameters (Np, St) relevant to the function or deterioration of the sensor are determined. A limiting value (Npg, Sti) is determined for each. The parameter is measured repeatedly. Growth in the values determined, is extrapolated over time. The duration of residual life, i.e. when the extrapolation goes beyond a limiting value, is determined. A limiting window is determined for permissible parameter values, using upper and lower limits (Npgo, Npgu, Stgo, Stgu). Extrapolation is based on linear regression. At least two parameters are used, the shortest result predicted, being taken as the life. Statistical error is determined. For an electrochemical sensor, relevant calibration parameters are employed. These are the null point (Np), gradient (St), impedance or response time of a pH- or oxygen sensor. Extrapolation and life determination take place after each recalibration.