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oscilloscope without wire ground

Started by Tobias Gadelha July 28, 2013
Is there any risk to use oscilloscope without wire ground? Because with wire ground there is a short circuit when I use GND on the line.
On Sun, 28 Jul 2013 11:49:54 -0700 (PDT), Tobias Gadelha
<tobiasgadelha@gmail.com> wrote:

>Is there any risk to use oscilloscope without wire ground? Because with wire ground there is a short circuit when I use GND on the line.
Simply ensure that your contact information is forwarded to <http://www.darwinawards.com/> for proper attribution. Thanks!
On 7/28/2013 2:49 PM, Tobias Gadelha wrote:
> Is there any risk to use oscilloscope without wire ground? Because with wire ground there is a short circuit when I use GND on the line. >
You shouldn't be touching your ground to line voltage.
Em domingo, 28 de julho de 2013 16h16min59s UTC-3, Tom Biasi  escreveu:
> On 7/28/2013 2:49 PM, Tobias Gadelha wrote: > > > Is there any risk to use oscilloscope without wire ground? Because with wire ground there is a short circuit when I use GND on the line. > > > > > You shouldn't be touching your ground to line voltage.
but I need measure line (L1) with reference in line(L2).
On Sun, 28 Jul 2013 12:50:23 -0700 (PDT), Tobias Gadelha
<tobiasgadelha@gmail.com> wrote:

>Em domingo, 28 de julho de 2013 16h16min59s UTC-3, Tom Biasi escreveu: >> On 7/28/2013 2:49 PM, Tobias Gadelha wrote: >> >> > Is there any risk to use oscilloscope without wire ground? Because with wire ground there is a short circuit when I use GND on the line. >> >> > >> >> You shouldn't be touching your ground to line voltage. > >but I need measure line (L1) with reference in line(L2).
Trick 1: Use a dual channel scope with two probes and display the difference. This is the regular way to do it. Trick 2: I have also done the GROUND removal trick, but I am an expert in electrocution. On my scope I mounted an extra connector to disconnect the green/yello wire momentarily. better you do Trick one I described above. w.
On Sun, 28 Jul 2013 22:19:13 +0200, Helmut Wabnig <hwabnig@.- ---
-.dotat> wrote:

>On Sun, 28 Jul 2013 12:50:23 -0700 (PDT), Tobias Gadelha ><tobiasgadelha@gmail.com> wrote: > >>Em domingo, 28 de julho de 2013 16h16min59s UTC-3, Tom Biasi escreveu: >>> On 7/28/2013 2:49 PM, Tobias Gadelha wrote: >>> >>> > Is there any risk to use oscilloscope without wire ground? Because with wire ground there is a short circuit when I use GND on the line. >>> >>> > >>> >>> You shouldn't be touching your ground to line voltage. >> >>but I need measure line (L1) with reference in line(L2). > >Trick 1: >Use a dual channel scope with two probes and display the difference. >This is the regular way to do it. > >Trick 2: >I have also done the GROUND removal trick, >but I am an expert in electrocution. >On my scope I mounted an extra connector to disconnect >the green/yello wire momentarily. > >better you do Trick one I described above. > >w.
Back in the 1977-1987 time-frame (OmniComp/GenRad days) I used to have a TEK probe that provided isolation from ground for such measurements, so that I could probe off-line switchers safely. You might want to track one of those down _before_ you electrocute yourself ;-) ...Jim Thompson -- | James E.Thompson | mens | | Analog Innovations | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | San Tan Valley, AZ 85142 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | I love to cook with wine. Sometimes I even put it in the food.
On Sun, 28 Jul 2013 12:50:23 -0700 (PDT), Tobias Gadelha
<tobiasgadelha@gmail.com> wrote:

>Em domingo, 28 de julho de 2013 16h16min59s UTC-3, Tom Biasi escreveu: >> On 7/28/2013 2:49 PM, Tobias Gadelha wrote: >> >> > Is there any risk to use oscilloscope without wire ground? Because with wire ground there is a short circuit when I use GND on the line. >> >> > >> >> You shouldn't be touching your ground to line voltage. > >but I need measure line (L1) with reference in line(L2).
--- Use a 2 channel scope which can invert one channel and add the two channels. Connect the grounds of both probes to mains ground, the channel which doesn't invert to L1, the channel which does invert to L2, invert the channel, and add the two channels. Also, it would be a good idea to set the sensitivity (volts per box) of both channels equal. Start off high and work down. -- JF
Tobias Gadelha has brought this to us :
> Is there any risk to use oscilloscope without wire ground? Because with wire > ground there is a short circuit when I use GND on the line.
The real answer is ___ You do not know enough to be fooling with mains power. IT WILL KILL YOU :-@ -- John G
On Sun, 28 Jul 2013 12:50:23 -0700 (PDT), Tobias Gadelha
<tobiasgadelha@gmail.com> wrote:

>Em domingo, 28 de julho de 2013 16h16min59s UTC-3, Tom Biasi escreveu: >> On 7/28/2013 2:49 PM, Tobias Gadelha wrote: >> >> > Is there any risk to use oscilloscope without wire ground? Because with wire ground there is a short circuit when I use GND on the line. >> >> > >> >> You shouldn't be touching your ground to line voltage. > >but I need measure line (L1) with reference in line(L2).
Use a small transformer to isolate and step down the voltage. Calibrate the ratio with a DVM. -- John Larkin Highland Technology Inc www.highlandtechnology.com jlarkin at highlandtechnology dot com Precision electronic instrumentation Picosecond-resolution Digital Delay and Pulse generators Custom timing and laser controllers Photonics and fiberoptic TTL data links VME analog, thermocouple, LVDT, synchro, tachometer Multichannel arbitrary waveform generators
"Tobias Gadelha"
> >> You shouldn't be touching your ground to line voltage. > > but I need measure line (L1) with reference in line(L2). >
** L1 or L2 will be at the almost same potential as ground - so you have no real problem. .... Phil