Longitudinal Wave Experiment to demonstrate Overunity

[Marsing]

Obviously the frequency counter is wrong. That's why one needs to look at and analyze the wave forms. When you do, you see that there is a single, poorly-shaped pulse on the output, and with the extremely low duty cycle, represents about 4W of actual output power (average).

Is there ripple causing significant power other than the obvious spikes? We would need to see the scope shot amplified in-between the pulses to know for sure.

Yes, the actual frequency is 4.2kHz, and hence the period T is 238us, not 250us.

Correct, thank for remind that, counter only count how many pulse in a second without caring where and when, exp: in 1 ms with ten pulses while other 999ms zero, completely wrong assuming there is 10hz where T=100ms.
i agree with you, we would need to see the scop shot, in this case in range 238uS during off state from main freq to find any potential ripple to be included in average output power.

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[TinselKoala]

"Please don't bother about A/C DC setting for virtual scope.Nothing different was observed related to waveform or position of waveform."

Utter facepalm. You still don't get it, do you. SELECTING AC COUPLING PLACES A CAPACITOR IN SERIES WITH THE SCOPE PROBE. How can you legitimately report power measurements when your instrument is connected THROUGH A CAPACITOR to your DUT? You cannot. Sorry to shout, but apparently demonstrations, illustrations, reference citations and even white papers from National Instruments are just not getting through to you.

If you truly truly see no difference when you are selecting AC vs DC coupling, that is +purely a coincidence+ caused by the symmetry and "ac nature" of your measured waveform. In the general case THIS WILL NOT BE TRUE, and for that reason DC-coupling should ALWAYS be used for power measurements and even for general scoposcopy. It is RARE to find a situation where AC-coupling is really the appropriate setting, and this set of experiments so far is not such a situation. If you proceed to look for the magnitude of ripple sitting on top of a stronger signal, that is one legitimate use of AC-coupled channels, but you will no longer be able to read your power reading from "numbers in boxes", you will actually have to interpret the trace itself.

[MarkE]

Assuming that the light bulb acts as a constant value resistor, which over the driven period of about 30us is reasonable, then the instantaneous power through the light bulb is: 

P_BULB = V_BULB²/R_BULB.

The energy across one cycle is the integral of the power across that cycle.  The cycles are just under 300us long. 

The circuit monitored by Ch. A is AC fed.  As only the voltage is being monitored across a resistor then DC coupling does not add any information.  Matters would be different if a current viewing resistor were being used to get the current.  But since it  is the bulb itself that is being used, an oscilloscope that is AC coupled with a cut-off frequency well below the repetition rate of 3.5kHz will yield almost identical voltage excursion across the bulb and power values as would a DC coupled measurement.  This is a special case. 

The input power measurement needs the addition of a current sense referred to the same DC reference as the input voltage measurement.  AC coupling either of those channels would yield erroneous power values.

AC coupling for power measurements does work under special circumstances as in the power output of MagPwr's set-up.  If one always DC couples, then one doesn't need to worry about whether their circumstances are such that AC coupling will or won't mess up the measurements.

[TinselKoala]

Hey, I always stop at stop signs, even when there is no other traffic. Apparently no other traffic, that is. Who knows, there may be a cop behind that billboard, or a car in my blind spot.

Just because sometimes I can run a stopsign with impunity, does not mean it's a recommended practice or even that it's OK to do it sometimes. Of course,  nobody dies when an oscilloscope is misused, usually.

[MarkE]

There is wisdom in always following best practices whenever possible.  It cuts down on errors due to faulty assumptions.  That helps avoid errors snowballing.  Thre is no good reason to AC couple here even thogu doing it on voltage only across the bulb won't make any noticeable difference.