Reactive power - Reactive Generator research from GotoLuc - discussion thread

[TinselKoala]

In that last set of scopeshots the "Ch2" baseline is not set exactly on the center graticule marker. It has a "slight" offset in the negative direction.

I know this seems very weird but I have encountered scopes that put the trace position offset into the math. If this scope behaves that way, then it might make a difference if you get both channel baselines exactly on the center graticule.

This would be a great time to check that, since that last set of traces is so close to being equalized but still has that little displacement of the Ch 2 baseline. Set up just exactly like that but use the vertical position control to get that baseline marker set right on the centerline, and then see if there is any difference between this set and that last set in terms of symmetry and absolute values for the Math.

[poynt99]

TK,

I just tried this, and shifting one trace up or down does make a difference in the computed MEAN power, as I noted back when I was doing the Ainslie tests, but there is still no change in the absolute value of the MEAN when I go from inverted to non-inverted on CH2.

Maybe the inverter amp (if they are using one) is just not matched that close on the TDS2004 as it is in other models.

[gotoluc]

In that last set of scopeshots the "Ch2" baseline is not set exactly on the center graticule marker. It has a "slight" offset in the negative direction.

I know this seems very weird but I have encountered scopes that put the trace position offset into the math. If this scope behaves that way, then it might make a difference if you get both channel baselines exactly on the center graticule.

This would be a great time to check that, since that last set of traces is so close to being equalized but still has that little displacement of the Ch 2 baseline. Set up just exactly like that but use the vertical position control to get that baseline marker set right on the centerline, and then see if there is any difference between this set and that last set in terms of symmetry and absolute values for the Math.

Good eye TK! ... my finger must of touch the adjustment at some point and didn't notice.

However, the math must detect that change as it make no difference to the Mean on this scope. I guess the scope needs to be re-calibrated somehow.

I could also use the average between Inverted and non Inverted if I need an accurate amount.

Luc

[poynt99]

Actually Luc, the more accurate is probably the non-inverted.

But I would hope the worst difference we would ever see would be 2% or so.

I don't know if there would be a calibration for this, but one could always contact Tektronix if necessary. My gut feeling is that the electronics which inverts the signal is what is causing the difference, and if that is the case, there should be a consistent percentage difference between the two settings.

One test you could perform would be to try CH3 and CH4 for the current probe (keep the voltage on CH1) and see what results you get with them.

[gotoluc]

Good idea!... I'll try channel 3 and 4 first.

I'll let you know the results

Luc