thanks , ill have purchased 30 membrane panels as a starting point , and will give the adc a go , to see if the "on" values are same ,then ill hammer one to death , see if it changes values radically , its the best way i can think of to see if there are issues

i think the speed and polling time will probably be more the undoing of the approach, with all the other things the pic has to do

cheers

sheldon