I tried the "The Differential capacitive transducer Twin-T measurement circuit" located at http://www.allaboutcircuits.com/vol_2/chpt_12/6.html without success. The article suggested that this was useful at "Capacitive transducers provide relatively small capacitances for a measurement circuit to operate with, typically in the picofarad range". Is there a suggestion for calculating resistance values based on specific capacitance value/ranges? Thanks in advance for any help you can provide.