pH sensor measurement

1 . A method for measuring the impedance of a pH sensor electrode comprising:

applying a positive voltage pulse to the pH electrode;

taking a plurality of samples of the electrode voltage response to the positive pulse, the samples being equally timed from each other during application of the positive pulse;

from those samples, estimating the impedance of the electrode;

applying a negative voltage pulse to cancel out induced charges from the positive voltage on the electrode so that the electrode quickly recovers to read media pH levels; and

wherein the negative pulse is dynamically adjusted as a function of the electrode voltage response.

2 . The method of claim 1 wherein the samples are taken within less than 250 ms of the beginning of the positive pulse.

3 . The method of claim 2 wherein three samples are taken equally spaced apart in time.

4 . The method of claim 3 wherein the three samples are taken before the asymptote of a curve of the electrode voltage response.

5 . The method of claim 1 wherein the width of the negative pulse is dynamically adjusted.

6 . The method of claim 5 wherein the width of the negative pulse is dynamically adjusted by:

determining the energy of the electrode voltage response after applying the positive pulse; and

generating a negative pulse that substantially matches the total energy of the electrode voltage response.

7 . The method of claim 6 wherein of the pulse width of the negative pulse is determined by the total energy of the electrode voltage Response divided by the voltage amplitude of the positive pulse.