This may have been asked. If you place a resistor of similar resistance to the salt solution across the probes at night and repeat in morning, do you get a shift in frequency , and if so, how much? Electrodes - Platinum wire? Russell On --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .