Simultaneous measurement of emf and short circuit current for a potentiometric sensor using perturbation technique

A scheme is proposed to measure the emf and short circuit current of a potentiometric sensor simultaneously. A small amplitude alternating square voltage pulse is applied across the electrodes and the respective currents are measured. From these currents, the open circuit potential (e(0)) and the short circuit current (i(s)), which are characteristic of the electrochemical cell are calculated. The effect of various parameters on the electrode polarisation is explored. The method is demonstrated using a solid electrolyte based potentiometric oxygen sensor with the configuration Pt, O-2 (sample) \CSZ\ O-2 (reference), Pt. To minimise the effect of electrode polarisation, the present approach is extended to accommodate variable voltage pulse amplitudes dynamically for successive pulse cycles as well as within each pulse cycle. The perturbation method and its progressive modifications are systematically developed and the corresponding theory is discussed in this paper. (C) 2004 Elsevier B.V. All rights reserved.