Testing the TK Tar Baby

[picowatt]

The FG's "negative" or black lead must have been hooked directly to the battery negative, the common circuit ground, for all of the experiments and demonstrations, because that was the way the apparatus was constructed. There is no evidence whatsoever that she had the FG's black lead in the correct location for any of the reported trials, and the evidence we DO have... the video of the demonstration... clearly shows it connected to the common circuit ground, the battery negative.

TK,

That is why I am always having to say "non-battery end of the CSR" or the "battery negative".

Obviously, if the FG signal ground is connected DIRECTLY to the battery negative, instead of to the non-battery end of the CSR, no DC or AC current flowing thru Q2 and the FG will be visible on the CSR trace.

Therefore:

Because all DC current flow thru Q2 is through the FG, all DC current will bypass the CSR and return directly to the battery negative.  No DC bias current will be measured at the CSR.

For AC currents, 80% or more of the AC current is through the MOSFET capacitances to the CSR, so that much of the total AC current will be indicated by the CSR trace.

The other less than 20% of the AC current that flows thru the FG will bypass the CSR and be returned directly to the battery negative and also not be measured at the CSR.

So, if the FG signal common is connected to the battery negative instead of the non-battery end of the CSR, all DC current and a bit less than 20% of the AC current flowig thru Q2 will bypass the CSR and not be measured or observed via the CSR trace.



On the other hand, if the FG signal common IS connected to the non-battery end of the CSR, then ALL DC and ALL AC currents will pass thru the CSR and be indicated by the CSR trace.

[picowatt]

Part 3.

First we look at an example of an open circuit FG setting of +/- 12V with 20% duty cycle. Once the FG is connected to the NERD circuit as shown, we see that not only is there a negative limit of -4V being created by R_OUT, but there is a positive limit of 10V as well, again because of a voltage drop across R_OUT. In this latter case, the current path is through Q2's forward-biased body diode. Here we see a current of 37mA.

During the negative portion of the FG output, the current is 160mA.

Next, we look at the current path while the FG output is positive. This is shown by the RED path. Note that without Q2's body diode, there would be no path. This is a closed-loop secondary path not including the battery. Once the FG output setting is below 10V, there is almost no current through this path.

Following this, we see the current path for a negative FG output. This is shown by the BLUE path. This path through the FG includes the battery and is part of the main current through the load. There is only -4V at the FG terminal due to the 160mA flowing through its 50 Ohm R_OUT, which constitutes an 8V voltage drop.

Next we take a look at the dynamics from end-to-end by imposing a DC sweep through the NERD circuit as shown in the simulation schematic. We are sweeping from -16V through to +16V to see where the limits are at each end. Also shown in red is the current through the 50 Ohm as a function of the sweep voltage.

.99

.99,

In your positive 12volt setting drawing (red path), it might have been better if you'd left the Q2 body diode path out of the mix for now.  I believe it is just confusing things.

Using ten volts to the gate of Q1, the Q2 body diode would not have been forward biased, but Q1 would have been fully on and the body diode path could have been omitted.

Also, in the red path drawing, why did you not show the full clockwise path thru the batteries, Rload, Q1, and the CSR as you did for the blue path drawing?  I believe that is adding confusion as well.

I would suggest eliminating the path thru the body diode for now and outline the full clockwise path in the red path drawing as you did for the blue path drawing.

From reading her responses, I believe it may be possible she believes the red/blue path drawings are depictig clockwise and anti-clockwise current flow instead of FG negative and positive output conditions.  The body diode path and lack of a full clockwise path around the battery in the red path drawing is, I believe, the source of confusion.

PW

ADDED:  In the red path drawing, consider showing the FG out going only to the Q1 gate with +10V out for the FG and indicating just leakage current for that path (1nanoamp or similar).  As well, draw in the full clockwise hi current path thru Q1 all the way around the batteries as you did in the blue path.  Then just stick with 5.5amps or so flowing when Q1 is on (red path) and 160ma. when Q2 is on (blue path).   

I realize you are attempting to show only the FG paths, but again, I believe she may be getting confused a bit.

[TinselKoala]

TK,

That is why I am always having to say "non-battery end of the CSR" or the "battery negative".

(snip, see original post)

So, if the FG signal common is connected to the battery negative instead of the non-battery end of the CSR, all DC current and a bit less than 20% of the AC current flowig thru Q2 will bypass the CSR and not be measured or observed via the CSR trace.

On the other hand, if the FG signal common IS connected to the non-battery end of the CSR, then ALL DC and ALL AC currents will pass thru the CSR and be indicated by the CSR trace.

Right. Now.... Say the FG signal common is connected to the transistor side of the CSR as is proper for the current measurement.
What if the FG signal common is connected to the chassis ground of the FG, which is connected back through the line cord to the mains ground, which is connected through the scope mains cord to the oscilloscope chassis ground which is connected to the scope probe ground leads which are connected to the battery negative? And if one oscilloscope is "isolated" by cutting off its main cord ground pin...yet that scope is connected in strict parallel with one which has not had its ground pin cut off... isn't the CSR shunt "shorted out" by the groundloop?

Regardless of that issue-- perhaps the FG signal ground is isolated (possible) and both scopes have isolated probe grounds (unlikely) -- nevertheless the location of the FG signal ground black cliplead during the reported tests should be confirmed.If it WAS on the transistor side of the shunt for the experimental trials... WHY was it moved to the incorrect location for the only photoshoot of a trial there is: the demo video? Can it be proven to be in the correct location for the reported experimental trials?

And if it WAS NOT on the transistor side of the shunt... then all the current data reported in the "papers" is obviously invalid. All of it.

[picowatt]

Right. Now.... Say the FG signal common is connected to the transistor side of the CSR as is proper for the current measurement.
What if the FG signal common is connected to the chassis ground of the FG, which is connected back through the line cord to the mains ground, which is connected through the scope mains cord to the oscilloscope chassis ground which is connected to the scope probe ground leads which are connected to the battery negative? And if one oscilloscope is "isolated" by cutting off its main cord ground pin...yet that scope is connected in strict parallel with one which has not had its ground pin cut off... isn't the CSR shunt "shorted out" by the groundloop?

Regardless of that issue-- perhaps the FG signal ground is isolated (possible) and both scopes have isolated probe grounds (unlikely) -- nevertheless the location of the FG signal ground black cliplead during the reported tests should be confirmed.If it WAS on the transistor side of the shunt for the experimental trials... WHY was it moved to the incorrect location for the only photoshoot of a trial there is: the demo video? Can it be proven to be in the correct location for the reported experimental trials?

And if it WAS NOT on the transistor side of the shunt... then all the current data reported in the "papers" is obviously invalid. All of it.

TK,

Yes, you are correct.  Neither scenario allows the CSR to account for all current flow.

That may be why the FG common was moved to the battery negative in the March demo.  Possibly it was originally connected to the xstr side of the CSR but it was noticed that the traces looked better with it on the batt neg instead.

If the FG common was connected to the batt neg then DC and AC currents flowing thru the FG would have bypassed the CSR and not be visible on the CSR trace. (Q1 current and the bulk of AC current would have been indicated on the CSR trace)

If the FG were connected to the xstr side of the CSR, and a low resistance path existed between the FG common and the 'scope grounds, the DC current read on the CSR trace would likely have been indicating low, depending on the DC resistance of the test leads, power leads,etc as compared to the value of Rshunt. 

But, for the AC osillations, one must also consider how much inductance might have existed in the path from FG common to 'scope ground as well.  But again, it would likely cause AC currents to indicate low on the CSR trace.

Neither of the above scenarios provides an accurate reading of all current flow. 

Obviously, conecting an isolated FG with its signal common connected to the xstr side of the CSR would have been more ideal. 

PW

[TinselKoala]

Yes.... I can recall some old discussion about the location of the cvr and the instrument ground leads but I don't remember if the real significance was stressed in those old days. I'm going to have to go back and look, document a timeline like I did for the revelation of the Q1-Q2 schematic by .99. 

I wonder if the IsoTech GFG8216a function generator has one of these: