Products > Test Equipment
REVIEW - Rigol DS2072 - First Impressions of the DS2000 series from Rigol
g2:
--- Quote from: Harvs on June 09, 2013, 06:52:12 am ---
--- Quote from: g2 on June 09, 2013, 05:36:31 am ---Dave's video is about measurement and connection to other electrical appliances, and what can happen.
When Rigol DS2072 is not grounded, it have 115 Volt (or 230 Volt) on chassis and also on probe tip.
Completely without being connected to other equipment.
All my old analog oscilloscopes I have had, do not have 230 V out on Chassis ground, and also on probe tip. And all other electrical instruments I have do not have it.
Rigol DS2072 must be bad isolated from main power(230V).
Are other digital oscilloscope brands also poorly insulated ?
Of course, it is best to ground.
--- End quote ---
So I just did a few checks. From measureing the mains input socket with an LCR meter, there's a common mode filter with 4.7nf caps between N-G and A-G. There's no blead resistance across the caps and ground (I am not saying there should be.)
So under controlled conditions I removed a ground, powered it up, and got what you described. This is as to be expected, the 4.7nf caps are forming a voltage divider to earth at the input CM filter, and so earth is now half way between neutral and active potentials. In Oz, with a 240V active and neutral at close enough to ground, this gives ~ 120VACrms on the jacks.
Shorting this to ground gives a current of 338uArms, which if you work out 1/(2*pi*f*C) on 4.7nf, and divide 240Vrms by it, you’ll get exactly that.
It’s got nothing at all to do with insulation, it’s designed that way to remove mains line noise (and vice versa.) So just operate it with a ground and you’ll be fine.
--- End quote ---
Thank you for testing and your explanation , Harvs, You are right !
I thought it was the special oscilloscope,
but it is then the switching power supply fault.
So it does not help to buy a second oscilloscope.
I returned the Rigol DS2072, maybe I should buy it again.
It seems to be a good oscilloscope.
Once again, thanks for the help!
marmad:
--- Quote from: g2 on June 09, 2013, 09:02:50 am ---When Rigol DS2072 is not grounded, it have 115 Volt (or 230 Volt) on chassis and also on probe tip.
Completely without being connected to other equipment.
All my old analog oscilloscopes I have had, do not have 230 V out on Chassis ground, and also on probe tip. And all other electrical instruments I have do not have it.
--- End quote ---
Do the other instruments have:
"WARNING: MAINTAIN GROUND TO AVOID ELECTRIC SHOCK"
engraved in large letters on them?
Harvs:
--- Quote from: g2 on June 09, 2013, 09:02:50 am ---I returned the Rigol DS2072, maybe I should buy it again.
--- End quote ---
:palm: I hope it didn't cost you anything to return it!
g2:
--- Quote from: marmad on June 09, 2013, 09:10:52 am ---
--- Quote from: g2 on June 09, 2013, 09:02:50 am ---When Rigol DS2072 is not grounded, it have 115 Volt (or 230 Volt) on chassis and also on probe tip.
Completely without being connected to other equipment.
All my old analog oscilloscopes I have had, do not have 230 V out on Chassis ground, and also on probe tip. And all other electrical instruments I have do not have it.
--- End quote ---
Do the other instruments have:
"WARNING: MAINTAIN GROUND TO AVOID ELECTRIC SHOCK"
engraved in large letters on them?
--- End quote ---
My old oscilloscope (Hitachi V-525) have it engraved, and I've never had it grounded.
And it's never been 115 or 230 V on its chassis.
Grounding was in the past for extra protection.
Now, it is obviously necessary.
As I have said before, in Denmark we were first grounding in new houses about 1995 (in wet room before). I would have been happy for a digital oscilloscope, who absolutely not have to be grounded.
Now Harvs come with the explanation why it does so.
marmad:
--- Quote from: g2 on June 09, 2013, 10:35:10 am ---Grounding was in the past for extra protection.
Now, it is obviously necessary.
As I have said before, in Denmark we were first grounding in new houses about 1995 (in wet room before). I would have been happy for a digital oscilloscope, who absolutely not have to be grounded.
--- End quote ---
Regardless of wiring in Danish houses, any electronics operated from switching power supplies need to be grounded - and always have. I noticed back in 1988 when I ran my PC without a ground connection that there was 110-120V potential on the metal case.
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