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AHA..

""What are we calculating wrong?? Check mine, I'll check yours""..John

I made an erroneous assumptions.

First, that the energy loss due to peltier effect would only occur on the leading edge of the sine wave..

While the heat gradient front is still travelling away from the junction, saturation has not occured..That will happen only when the heat capacity of the local area has been "filled", so to speak. The thermocouples that are small enough for bee use could be considered to test that part at 10 to 100 hz frequencies. So, without saturation, the peltier effect will still apply to the trailing edge of the waveform. That will fall apart most likely at or near the zero crossing, where the current slew rate is the greatest (the current travels too fast for the thermal to follow). Only for the high slew rate end of sine pulse signal portion can seebeck happen.

So, that would mean that the bulk of the dissipation is going to be a function of current only. And that will occur at the fundamental frequency..It may be that the seebeck return energy is the actual distortion mechanism, as it can only occur near the zero crossings.

Does a small pulse train of return energy occuring just before zero crossing match in any way the spectra that is being observed by JC?

Can the drive signal be modified so that the trailing edge is faster, thereby stopping peltier during the drop, and forcing more seebeck to be measured?

(That is why I chose the IA approach rather than the typical 1700B approach...I will be able to handle non sine waveforms, relying instead on the IA CMMR to pull the drive out.)

By looking at the whole loop: 600 ohms in series with a current dependent dissipation:

The power delivered to the load is V^2 / R.

The current in the loop is V/R, therefore the peltier diss goes as V.

As the signal increases, the ratio of loss to signal goes as V / V^2, or 1 / V.

Meaning, as the signal voltage increases, the distortion level goes down.

Does a 1 / V relationship match the way the distortion being measured drops down? As I recall, JC said it did go down as he increased the signal, but did not specify the mathematical relationship.

Cheers, John


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