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Need help: spikes in current measurement signal conditioning circuitry

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duak:
Perhaps the oscilloscope has an Hieronymous Effect sensor:  https://en.wikipedia.org/wiki/Hieronymus_machine

Balage, are the two cables from the circuit to the oscilloscope the same length and beside each other?  I wonder if there is any chance that the two cables form a loop with the switched line current passing through the center.  This might explain why one is inverted.

StillTrying:
I think there's quite a bit of evidence that it's the scope or the probing, and that you'd be better off with 2 proper scope probes and the scope about 1 meter away before asking Rohde, but if you do end up asking them let us know what they say!

chuckb:
Something caught my eye.
The scope display is showing 40V / division with coax inputs, 1:1 probes. I would expect there to be a maximum of 10V / div with 1:1 probes.

The manual lists 100V / division max when using 10:1 probes. So with coax I'm guessing that the max will be 10V / div. This scope does not automatically compensate when probes with different attenuation are installed so there has to be a manual setting somewhere in the menus.

The two channels are electrically isolated from each other so it may help reject high freq noise if the BNC connectors are electrically connected with a strap right at the scope.
Good Luck!

balage:

--- Quote from: duak on July 31, 2019, 04:51:59 pm ---Perhaps the oscilloscope has an Hieronymous Effect sensor:  https://en.wikipedia.org/wiki/Hieronymus_machine

Balage, are the two cables from the circuit to the oscilloscope the same length and beside each other?  I wonder if there is any chance that the two cables form a loop with the switched line current passing through the center.  This might explain why one is inverted.

--- End quote ---

There is the "RTH-B99: Advanced Hieronymous Effect sensor" option installed.  :o This is a must have feature.

The cables were run beside each other, yes.


--- Quote from: StillTrying on July 31, 2019, 05:28:30 pm ---I think there's quite a bit of evidence that it's the scope or the probing, and that you'd be better off with 2 proper scope probes and the scope about 1 meter away before asking Rohde, but if you do end up asking them let us know what they say!

--- End quote ---

I will let you know the consequences of course!

StillTrying:

--- Quote from: balage on August 01, 2019, 07:46:07 am ---I will let you know the consequences of course!

--- End quote ---

What was the answer to the inverted trace in Reply#11. I'll bet it was something to do with the scope's isolated channels. :)

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