Products > Test Equipment
REVIEW - Rigol DS2072 - First Impressions of the DS2000 series from Rigol
Hydrawerk:
Well, I am not sure, someone told me that the trigger indicator is always visible on TDS2000 scopes... :-//
g2:
--- Quote from: Hydrawerk on June 08, 2013, 11:01:41 pm ---Same as on my DSOX2002A and my father's DSOX3000 at his company. It's probably not a bug.
--- End quote ---
Thank you for testing. But it just tell that all Rigol oscilloscopes, is real bad isolated from main power(230V).
g2:
--- Quote from: marmad on June 08, 2013, 10:33:25 pm ---
--- Quote from: g2 on June 08, 2013, 08:22:36 pm ---I have had a Rigol DS2072 and I Got An Electric Shock from it.
I was using a 2 wire extension cord without ground (earth).
I found out when Rigol DS2072 is not grounded, there is 115 volt on Chassis ground,
and independently of the switch are On or Off.
Is it only my Rigol DS2072 that is defective ?
How are other digital oscilloscopes ?
Do I have to change the house's electrical installation with ground (earth) ?
--- End quote ---
Other oscilloscopes are the same (except for specially-built ones with isolation - I have a Tektronix battery-operated analog scope that is double-insulated). What you were doing is dangerous - and there is lots of information about it online; the DSO MUST be grounded.
Dave even made a video which talks about the fact that the DSO chassis (and all BNC connectors) are shorted to Earth ground (and how to avoid accidents when probing).
--- End quote ---
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.
Harvs:
--- 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.
Harvs:
To answer the second part of your question, is it common? Yes, very. It's needed to meet EMI/EMC compliance when you've got a switching power supply.
Attached is a photo of the IEC input socket on a high end computer power supply I happen to have in pieces. You can also see here they've done exactly the same thing. If I connected this PC without a ground, I'd have 120Vrms on the PC case.
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