Floating the 'scope
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From: Michael A. Terrell on 8 Mar 2010 11:46 George Herold wrote: > > Michael A. Terrell wrote: > > > > Good for you. That would get you fired any place I've ever worked. > > If you needed isolation, you plugged whatever you were working on into > > an isolation transformer. If OSHA found a cord like that, the company > > would be fined and it could run into thousands of dollars. > > Thanks Michael, The isolation transformer is on order. Good deal! Just don't get careless when using it. :) -- Greed is the root of all eBay.
From: John Larkin on 8 Mar 2010 13:26 On Mon, 08 Mar 2010 08:57:54 -0800, Fred Abse <excretatauris(a)invalid.invalid> wrote: >On Mon, 08 Mar 2010 08:29:57 -0800, John Larkin wrote: > >> That's like using two probes in A-B mode. The equivalentcommon-mode rrange >> is small, because the internal amps saturate at the equivalent of a couple >> of screens worth of offset. > >Pretty much what I said. > > >> The TPS can show tou a 10 millivolt signal >> riding on the AC line, with 200 MHz bandwidth. > >With only 8 bit resolution? 8 bits is pretty good at 10 mV/div riding on 120 RMS. Kick in signal averaging and you can resolve microvolts. Signal averaging is magic. Hey, this is 2010! John
From: George Herold on 8 Mar 2010 15:29 On Mar 8, 11:46 am, "Michael A. Terrell" <mike.terr...(a)earthlink.net> wrote: > George Herold wrote: > > > Michael A. Terrell wrote: > > > > Good for you. That would get you fired any place I've ever worked. > > > If you needed isolation, you plugged whatever you were working on into > > > an isolation transformer. If OSHA found a cord like that, the company > > > would be fined and it could run into thousands of dollars. > > > Thanks Michael, The isolation transformer is on order. > > Good deal! Just don't get careless when using it. :) > > -- > Greed is the root of all eBay. Yeah well Phil A. hasn't answered, but it seems that even with the scope plugged into an isolation transformer, you can still get 'whacked' if you attach the probe 'ground' to the wrong spot. George H.
From: Paul E. Schoen on 8 Mar 2010 18:21 "John Larkin" <jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote in message news:ng9ap5p9o12bl6eekp5a1lujmiubsab8i3(a)4ax.com... > On Mon, 8 Mar 2010 07:53:52 -0800 (PST), George Herold > <ggherold(a)gmail.com> wrote: > >> >>Digital scopes use to have terrible user interfaces. But they are so >>much better now. The colored knobs are associated with the trace >>color. It's so easy to know which knob to grab... try it you may >>like it. >> >>George H. > > Yeah, some of the early digital scopes, especially the HPs, were > nightmares to drive. It turns out that the classic arrangement of > knobs is best, so most digital scopes now resemble old analog scopes. Way back in 1989 I decided to buy a DSO, and I had been working at a company that was a distributor for Tektronix, so I was able to evaluate one of their scopes and I could have gotten it at cost. But I found the interface very confusing and frustrating. In general, I liked HP's panel layout better than Tek's. But I think the HP DSOs were too pricey for my budget. I ended up purchasing a Hitachi VC-6025, for something like $2000, and it is still working perfectly. It meets all my needs and I find the user interface simple and comprehensive. At that time I also had used a LeCroy digital scope, which was nice, but hugely expensive. And I also used a Data Precision waveform analyzer, which was also very expensive, but we needed the high accuracy and the math functions such as true RMS of portions of the waveform between cursors. We didn't need high frequency response, as we were measuring mains AC voltages and currents at 60 Hz. But we were developing instrumentation rated at 1% accuracy, so we needed 0.25% or better for our standard. Prior to the DSOs and waveform analyzers, back in 1975-1979 when I was first working on this class of instrumentation, we bought a Visicorder from Government Surplus to observe the waveforms of the current pulses we needed to analyze. That was fun, loading up rolls of photosensitive paper, and timing the start of the recorder with the test set, and then going through the pile of paper and trying to make accurate guesstimates of RMS value and time. Ah, the good old days... Paul
From: Paul E. Schoen on 8 Mar 2010 18:29
"Fred Abse" <excretatauris(a)invalid.invalid> wrote in message news:pan.2010.03.08.19.42.06.287699(a)invalid.invalid... > > I'd still be happier with 12 bits, but then I just don't like digital. I > always feel like I wanna see between the samples ;-) Cubic (or polynomial) spline curve fitting. http://en.wikipedia.org/wiki/Spline_(mathematics) Of course, you can never be sure that the waveform didn't go bonkers between two samples! Paul |