Instead of using a 7555 or 4093 oscillator why not just
do it direct from the PIC measuring the RC period?
It saves one external chip and gives total control of
your probe current waveform to reduce oxidation.
-Roman


Marco Genovesi wrote:

> For the moment, I wouldn't use a current regulator, so I'm thinking to use a
> CMOS 555 timer ( I imagine that it has a much more stable osc frequency
> versus power supply voltage), but I don't understand if  the squarewave
> produced with a 555 and 4093 can be "comparable" (final scope is to prevent
> probe oxidation:  I need a real A.C. current?? ).

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