Reactive power - Reactive Generator research from GotoLuc - discussion thread

[tinman]

So here is what i did ,just to lead myself up the garden path a bit. I took the Crms of ch2,which is 168 mV,over our .1 ohm resistor,and come up with a current of 1.68 amp's. then multiplied 1.68 x the Crms of ch1 of 66 volt's. This comes to 110.88 watt's. My watt meter says the motor draws 48 watts without the exciter circuit conected,and 158 watts with the exciter circuit conected. 158-48=110-Oh by the way-all the above scope shots are taken on the exciter circuit-just as a demo.

[poynt99]

Okay, here you go.

I'm done for the night

Luc

OK, still off a bit.

I guess we'll see if any of those other settings are different.

I wonder if it could be the probe you are using. I am not even using a probe, rather a length of coax with a BNC on one end, and alligator clips on the other.

One thing you may try is changing the termination from 1M to 50 Ohm for the current probe channel.

[poynt99]

I can also get all this junk(below),but only on ch1 and ch2,not math.
As you can see,i realy know my way around a scope.

LOL. Well the good news is, that you can do A x B and display it! I don't think we were able to do that several months ago.

So the challenge now is to figure out if you can apply a measurement to the MATH trace. But I suspect that is what you are struggling with at the moment, correct?

I see that you have a MEAN measurement in that mess of numbers, but you say you can't get that for the MATH trace? Hmm. Damn, having the MATH trace is almost useless if you can't apply any measurements to it!

[poynt99]

Channel Settings:
- Termination = 1M
- Offset: 0.0V, 0.0A
- Leave the vertical scaling to default for now.

Acquire Menu:
- Record Length = 10k


Okay but all the above I don't see in menus?

- OK, You don't have the choice of termination on your scope. 1M is the fixed setting.

- Looks like offset is not included. Good.

- Vertical scaling, I will try it with mine and see what effect if any it has.

- Record Length seems to be fixed at 2500. So no adjustment there.

So I think you have it adjusted as best we can get it for our needs. I am going to perform a similar test you just did above to see how close my measurements correlate when inverting CH2.

[poynt99]

Luc,

Just for curiosity sake, try running the calibration again, but this time leave the voltage and current probes connected to the scope. Disconnect them from the circuit though and run the cal. Do this once with the probes open-circuited, then remeasure to observe the balance, and once with the probe tip shorted to the gnd lead. Again remeasure to see if the inverted and non-inverted are any closer.

Hopefully one of these two methods will minimize the slight offset we are seeing. Let me know what you find.

I have done this before, and even though the instructions say to disconnect the probes, I have found that passive probes can sometimes cause some sort of offset, and calibrating with them attached removes this offset.