Liquid electrolytic conductivity measurement - has multiplexer which selects precision resistances for measurement of alternating current between stray field measurement electrodes

摘要

Current is passed through the liq. between outer and inner electrodes (1,5) on a thin-film substrate. The earthed inner electrode (5) is surrounded by an inner measuring ring (4) and two zigzag outer rings (2,3) which contact the liq. at two and three points respectively. The ends of the outer rings (2,3) are brought out to connection pads (6). The microcontroller provides periodic or aperiodic square or triangular waves, sinewaves or pulses up to 10V at audio frequency. ADVANTAGE - Procedure is reduced to purely ohmic measurement uninfluenced by polarisation, phase shift, line resistances or specific conductivity.