Method for detecting the need for calibrating probes

Abstract

An in situ probe failure detection method for probes which deliver an electric signal on account of a change of the concentration of a substance to be measured. An example of such a probe failure may be caused by, for example, fouling of the membrane as the relative change in signal may be interpreted as a change in the concentration of the substance to be measured. More particularly, the method involves detecting the need for calibrating probes, which probes deliver an electric signal on account of a change of the concentration of a substance to be measured, characterized by: (a) subjecting the probe to a stepwise change of the concentration of the substance to be measured; (b) calculating the value of the probe response time constant t.sub.c of the obtained measurement curve with the help of the following main equation (1): t.sub.c dy/dt=-y+.alpha..sub.0 +.alpha..sub.1 t wherein t=time (time), t.sub.c =probe response time constant (time), y=substrate probe signal (mass volume.sup.-1), .alpha..sub.0 =substrate concentration at start of response (mass volume.sup.-1), .alpha..sub.1 =rate of change of substrate concentration (mass volume.sup.-1 time.sup.-1), and (c) comparing the calculated t.sub.c values of at least two different measurements with each other, and in case the calculated t.sub.c values do not match, calibrating the probe.

Dependencies are inferred from the claim text.