In message <4.1.19990215113455.04664ed0@192.168.0.1>, dave vanhorn writes >At 02:21 PM 2/15/99 +0100, marcel wrote: >>Yes this is the reason that many of us disconnect the earth wire from the >>mains plug of the scope or use >>a transformer to separate the circuits if you do measurement on >>television set's mains voltage is >>sometimes on the chassis. > >Those of us who want to live past next week, use an isolation transformer >for the equipment being tested, and let the scope ground stay right where >it is. It's common practice to disconnect the earth wire to oscilloscopes, it's far safer than leaving it connected, if connected you have a potential 230v (in Europe!) across your hands when you try to connect the earth lead from the scope to the item under test. By disconnecting the earth lead you remove this serious hazard, this only leaves the unlikely breakdown of the scope mains transformer as a potential hazard. I've been repairing domestic electronic equipment for 27 years, I wouldn't use a scope with an earth lead, it's too dangerous!. Remember, we are talking about professional engineers here, not members of the public, we should be able to adopt safe working practices - and this doesn't include earthed test equipment (at least in most domestic cases). BTW, we use isolation transformers for feeding all the service benches at work (I ordered and installed them!), but I still consider an un- earthed oscilloscope an essential safety feature. -- Nigel. /--------------------------------------------------------------\ | Nigel Goodwin | Internet : nigelg@lpilsley.demon.co.uk | | Lower Pilsley | Web Page : http://www.lpilsley.demon.co.uk | | Chesterfield | Official site for Shin Ki Ju Jitsu | | England | | \--------------------------------------------------------------/