OP said his probes were in salt water. Salt water corrodes/oxydizes. His electrode impedance (R and or C) is changing because of corrosion. If he pulls the electrodes out of the water, washes them clean, then measures again, hours later, he will likely see less change, proving the postulate. Can he try changing out the water for distilled during the overnight period= ? Does the effect continue over time or flat line after a day or two or 3 without activation of the circuit? Does running the circuit reverse the effect? You have to eliminate chemistry effects and he hasn't said what kind of electrodes he's using so I'm betting corrosion effects. Robert On Tue, Sep 9, 2014 at 10:09 PM, John Gardner wrote: > Ravi - > > If you have the means to measure small currents, you might > > measure the current flowing through a diode and resistor (in > > series with a battery), taking care that the resistor value limits > > diode current to reasonable values... > > You'll see quite a difference between measurements in early > > morning, and those taken in the heat of the day... > > Of course all the components in your test are affected, including > > the measuring equipment... > > Jack > -- > http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist > --=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 .