A TRANSIMPEDANCE CONVERTER FOR LOW-FREQUENCY, HIGH-IMPEDANCE MEASUREMENTS

A straightforward but unique current to voltage converter is described which, in conjunction with a standard frequency response analyser (FR A), allows impedance measurements to be performed. The circuit topolog y minimizes the effects of parasitic impedance components enabling the quantitative measurements of high-impedance elements into the gigohm region-a feature not found on standard impedance bridges. This capabil ity has application in areas such as measurements on ion selective ele ctrodes. The combined facility provides a generally useful impedance a nalyser. However, its immediate utility was in the study of low-freque ncy electrode-electrolyte systems, to which the data presented relate. The circuit provides accuracy and stability, and is inexpensive to co nstruct from readily available components.