Cheers Mike. I've just seen those Fritz diagram around here before, so I thought they were the standard, although admitedly not clear. I'll have to do a schematics sheet anyway so I'll post that next.
I've seen a lot of people here use the word random or 'noise' when referring to the floating input. Hence my concern when I saw a distinct pattern - not that I thought it would affect anything, I just didn't like not knowing the cause.
Didn't realise until this week that piezos would cause mor etrouble than FDRs. Too late to go there now, but I will investigate and include in the critical analysis. Thanks for that.
