andy sir
thanks for telling me about the AC signalling ...
currently i am using 8 probes connected to the P1 of the processor and i am not feeding any high pulse to it .. along with these 8 probes i am having 1 common ground connection running along with them which will pull low the probe voltage ...
now after your mail i am wondering if i just use a SPDT relay and connec the common of relay once to gnd while sensing the probe status and for other times connect it to VCC .. will it solve the problem of electrolysis ??? but the next problem will be the clicking noise of the relays ... always working ....
please guide me more on this ...

thanks and regards
nitin