Is joule thief circuit gets overunity?

[TinselKoala]

Very nice clean analog waveforms Poynt.  Even though your new high-end DSO is amazing, if I had a bench I would still have an analog scope to compliment the DSO.  I know we have had this conversation before!  For example, at the bottom of the "fang" in the current waveform, you can see some tiny vestigial spikes.  So you crank up the intensity for a few seconds to make the vestigial spikes more visible.  Then you can hunt down the source of those spikes if need be.  You would have a hard time doing that with a DSO, you might note even realize that they were there.

I am not really following here but it would seem to me that the current only flows in one direction.  When you look at the schematic and analyze it, one would suppose that the logical conclusion is that the current should only flow in one direction.  So the bench and the circuit analysis are in accord.  I fear that Lawrence is chasing rainbows but the sky is clearing up now.

Yah. A 400 dollar brand new DSO might be nice..... but that same 400 dollars will buy a _lot_ of power and bandwidth in a good used, analog scope.

[picowatt]

Lawrence, I would recommend you try to find out why your scope consistently shows a 12-13mV offset when measuring the input current. I would like to see that scope shot duplicated and show the LED as well. It sure appears that the circuit is OFF.

Also, did you do any number crunching on my data from board #33? What were the results?

What is your comment on my scope results? How do you explain that the current never crosses the 0-ref line?

.99,

Lawrence's offset looks much better in his shorted probe shots.  Please note however that he said he hit the "default settings" button first, and as well, the traces are positioned to the center of the graticule.  Please recall that the DC offset specs I posted for the ADS1102CAL model scope used the "offset", i.e., the position of the trace relative to the graticule center (as I understood it), in the formula for the DC offset specification.

It would be intersting to have Lawrence use his scope as he usually does and demostrate that the input current swings above the zero line, and then perform the same measurement, but first pressing the "default setting" button, which I assume is what centered up his traces and whatever else I will have to read the manual.

Alternately, if he postioned the trace downward one full division (about where he normally positions the current traces), possibly the observed offset would increase.

I'll see what the manual says about the "default setting" when I get a chance...

PW

[TinselKoala]

For sixty one dollars, you get 5 preselected/defined voltage levels of your choice, good to five or six significant digits of precision, with free recalibration for two years.

http://www.voltagestandard.com/PentaRef.html
http://shop.voltagestandard.com/product.sc?productId=4&categoryId=1

This seems like it would be a very good investment for someone who is claiming OU results that depend on voltage measurements of 20 mV or less, with a measurement system that has clear artefactual errors.

[picowatt]

See that little "B" next to the channel setting indication in the shot of the shorted probes? That means that "bandwidth limitation" is set for that channel, which is excessively noisy and shows a definite DC offset.

Lawrence, please DO NOT use the scope's "auto setup" or Default Setup function for these traces! Clearly your scope should be set to the EXACT same settings, including BW limit OFF, for the probe and DC offset tests as it is set when you are making your measurements on a board! Set your scope MANUALLY and use its functions to SAVE the setup, then use the SAME setup for your measurements and for your probe/offset testing. DO NOT USE BANDWIDTH LIMITING, unless you also are using it when making your live measurements !!

I think .99 has asked you to make some actual measurements of small DC voltages, KNOWN small voltages like those that come from a voltage standard source like a LM199 chip or this unit here:
http://www.voltagestandard.com/Home_Page_JO2U.html
A test like this will be better than simply shorting the probe, as the degree of offset clearly depends on the voltage applied to the probe (from your own data which show this effect.)

And YET AGAIN, I am asking you to tell us the cause for the LARGE voltage discrepancy from one probe-channel combination that you illustrated when we first started exploring the probe compensation issue. You have never told us how that discrepancy happened, how it was resolved, and you haven't shown traces that prove that this issue has been fixed.

Also... high-end DSOs and DPSOs automatically detect the probe attenuation setting, but the Atten DSO does not. There is no way on the screen to tell whether or not the probe is set to 10x attenuation or 1x attenuation or that the scope's setting matches the probe setting. Are we quite assured that the scope and the probe have the same attenuation setting for that May 1 set of scopeshots?

TK,

Possibly that channel is noisey with or without the BW limit on, the BW filter is noisey, or he has a probe issue.  One would normally expect less noise with the BW limit on.

I looked at default setup in the manual, he adjusted a few things after pressing default setup, such as vertical sensitivity, etc.  Look in appendix C for the rather lengthy list of default settings.

PW

[picowatt]

Yah. A 400 dollar brand new DSO might be nice..... but that same 400 dollars will buy a _lot_ of power and bandwidth in a good used, analog scope.

TK,

Once again, the romance with analog...

The digital scopes seem to be going thru "bandwidth" wars similar to the digital camera "pixel count" wars.

I'd gladly accept a 200MHz BW limit in exchange for 16 bits of native vertical resolution (and 18bit enhanced).  Although 20-24bit would be, well, wow.  The extra dynamic range would be great for looking at noise and the FFT's would go down into the dirt.

I can currently only go 5MHz with 16bit resolution, above that, I have to go analog.

PW