Do I need to power my DSO via an isolating xformer

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triplej

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Joined 2011
#1
Hello, I have always powered my trusty analogue scope via an isolating transformer to avoid grounding one side of a floating power supply (for example) when measuring. Do people do the same for their DSO's? Model in question is the Hantek DSO2C10.
 
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#2
The hankek internal switching power supply needs the system ground of the mains to do it´s mains filtering. Isolating the ground may lead those filtering currents into the DUT. In the most sensitive gain settings I can see some residual of it`s own power supply on my scope - remied with oversampling/averaging.
 
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#3
Very good question. Had me thinking out loud. Assumption is that things are the same together with what basreflex wrote so apparently a small step back.

Could it that today special devices are produced for floating measurements!? Like the differential analogue scopes for mains measurements were?
 
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#6
I once built a PLL receiver to pick up cardiac fm modulated signals through seawater at 20Khz carrier. It was 30nV sensitive (2SK146 input stage with input stepup transformer, input eq noise resistance of 10 ohms) ) , but I had to build an isolation transformer on the R&S generator signal output to isolate the ground noise. Originally meant to pickup whale cardiac signals, later to show pacemaker activity response on swimmers.
 
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#9
Later we raced through alaska to find sleeping humpbacks (these are no guitar pickups) near petersburg alaska. Eventually we managed with the help of newfoundland fishermen and a marine biologist, who helped a whale trapped in their nets. (just to do a comparative study of the mammal heart and it's AV delay)
 
#10
availlyrics said:
Its always a good idea, I use isolation transformer for my DSO
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Except that the oscilloscope is now referenced to whatever the probe is clipped to. This includes ALL exposed metal, other channel BNC barrel etc. Even worse if you connect the probe to a high voltage, which would have burnt the probe input, but at least the earth would have saved your life. This is very much like disconnecting the scope earth wire in the plug, a trick that has hurt a few people I know
 
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#11
triplej said:
Possibly. Think if I'd known this i would have gone for a portable. I'm surprised more people haven't blown stuff up with the PE grounded probe lead.
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It is one of often misunderstood items. It seems everyone needs to make the mistake at least once just to understand. Same category: current transformers without load, tube amplifier output transformers without load, testing of ignition coils, microwave transformers. Often inductive items, not by coincidence.
 
#14
Thanks for the reference. I was aware of the risks but great to flag them. Don't work on dangerous voltages these days. Or if I do it's with DMM's. So the choices are, have a foreign earth influence readings (even with battery operated), have an unsafe test rig, or invest in a (no doubt) expensive isolation amplifier? Wowser.
 
#17
Huh?! That is the correct way so with separation of N and PE. Then the GND of the oscilloscopes input floats and is on the same potential of the point it is connected with. This can be a lethal voltage but without the isolation transformer the scopes GND is connected with PE = a short circuit.

However as can be read it does not work out well with digital/LCD oscilloscopes because of their internal SMPS that needs PE for its filtering.
 
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#19
How many times does the average DIYer need to measure mains circuits in circuit?

I had a differential input oscilloscope for that but sold it as it did not get much use. Of course one needs one the week after it is sold.
 
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