DESIGN OF A MINIATURE ELECTROLYTE CONDUCTIVITY PROBE USING ISFETS IN A 4 POINT CONFIGURATION

In this work the design fabrication and testing of a four point electr ode configuration based on ISFETs for the measurement of electrolytic conductivity are presented. The final design uses a distance between t he ISFET gates of only 100 mum allowing a chip area in contact with th e electrolyte of 2.2 X 2.2 mm. KCl electrolyte concentrations ranging from 0.1 mM to 1 M were used for testing the designed probe. Measureme nt results show a linear dependence of the output voltage of the ampli fier on the electrolyte concentration.