hi all,ive just noticed my scope doing wierd things when i probe the -ve lead of my bench psu,the trace showed about 10vd measured between my bench psu negative lead and my scope ground,any ideas?,also if i grab the probe tip i get about a 20v p2p reading like noise,if i grab my electric cooker chassis at the same time i get 0,is my house wireing iffy or my scope,its a pme system on the house,cheers m3vuv.