COP 20.00 (2000%) Times, Reactive Power Energy Source Generator,

[TinselKoala]

Hi Tinselkoala,

The Rigol scope is only a day old and so I am still learning its operation.

The differential probe has x20, x50 & x200 selections. I kept the x200 setting as I cant make the comparison with the x10 ground probe, exactly as you requested.

The previous shot before was done quickly as to not disturb my setup, henec the use of Chl2 & Chl3. The rigol measurement functions are over whole cycles so any display that shows less than a whole cycle results in blanked fields.

The phase shift according to the measurement function is 0.865deg.

When I tried to increase my vertical resolution from 20V to 10V there was an overange situation.

I tried the setup on my old Owon scope and set the max resolution I could, and measured 10us (approx 0.2deg) skew between the probes.

Which ever one you take,  0.865deg or 0.2deg  the skew is under a degree and so has little effect on the AxB (VxA) function computation.

Barry

Heh.. Now I'm convinced! Thanks for taking the time to do that. I can believe around 1 degree of difference between the active and passive probes at that slow frequency, and it will be the diff probe lagging of course. It might be interesting (but not really relevant here) to repeat that comparison at a much higher frequency to see if the scope's measurements of the shift changes at all. I would expect the phase angle between the Diff probe and the passive probe to increase with increasing frequency.


So here you've compared the Differential Voltage probe with a passive probe, right? And you've shown that the phase shift is very small. That's great! Now you should do the same thing with your current clamp probe, comparing the signal from it and from a passive probe across a current-viewing resistor in series with the circuit you are measuring with the current clamp.

Really, we want to see if there is a phase shift between the current clamp probe and the differential voltage probe. So by comparing both of them separately to a standard (the passive probe) you can get an idea if there is a shift introduced by your measurement.

I'm convinced that the shift from the Diff probe is small compared to the passive probe, but even such a small shift will have a measurable effect on the power function when near 90 degrees.


So if you could please do the comparison between the Current Clamp, and the passive probe looking at a CVR, then we'll know for sure that your measurements aren't introducing any phase shift into the computation of the power function.


I'm taking for granted that you have properly adjusted the compensation caps on your passive probes, etc.


Again, thanks for taking the time and trouble to perform these calibrations. I'm really jealous of your new scope; I wish I had a modern DSO in my lab to play with. In a pinch I can borrow a high-end Tek scope but it's kind of a hassle, involving 4 or 5 hours of driving.



--TK

[Void]

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[TinselKoala]

@listener191:
On the Owon scope, you have the baselines set 2 minor divisions apart vertically. If you look where the zero crossings are you can see that if the lower trace were raised up 2 minor divisions to compensate for the baseline difference, there would still be one minor division vertical separation at the zero crossings. There is a measurable shift shown on the traces on the Owon scope.
For the best visual quantitative interpretation, and even for proper math computations on some scopes, both channels of concern should be set to the _same_  center graticule baseline, very accurately. If you want to separate the traces for some reason, like qualitative examination of waveform shapes or etc, _please_ set the baselines directly on major graticule markers, to aid in visual interpretation of the traces.

Also it's a lot easier to read the thread if you limit your images to under 1024 pixels wide!

[listener191]

Hi Tinselkoala,

As I said previously to Farmhand, I have already posted details of the current clamp and it shows no appreciable skew.

Barry

[listener191]

Hi Void,

No the switching arrangement is the one I posted not Marios. Mario uses two switches on his original scheme because he uses a sound card to generate the pulses and he could not mix the channels onto a single bidirectional switch.

Barry