Testing the TK Tar Baby

[TinselKoala]

Preparing for the laborious process of manual multiplication and integration..... I got lucky and the scope shot was "perfectly" aligned horizontally and vertically in the camera frame !!

So I used mtPaint to overlay a rectangular grid on the traces, put in some reference lines, and started to identify time-synchronous values on each trace for multiplication and plotting in a spreadsheet.

This will take a while to complete, obviously, and I'll probably double the time resolution from what I show here, and I'll probably be able to do two complete cycles before I fkn freak out completely and go blind or something.

Horizontal purple line is the zero line for the top, current, trace and is the battery voltage for the bottom trace (the zero level is below the image frame), and the top is at 2 volts/div and the bottom is at 20 volts/div. The vertical grid is aligned fairly well with the graticle marks on the screen and is spaced at as close to double the screen marks as I could get it, so 10 volts per overlay grid division on the bottom trace and 1 volt per overlay grid division on the top trace.

[poynt99]

TK,

Don't waste your time doing the integration. Most of Rosemary's shots are of an averaged (MEAN) p(t) of the product of those two traces. See the attached as a good example.

Just multiply x number of fine points and take the average. If the result is a significant negative number, you're done. In the attached example (same shot from the paper), the MEAN p(t) is -73.4VV.

Also, remember that you are multiplying DC values, not just the relative p-p values. I mention this, even though I know you are aware of this, because your scope shot does not show the zero line for the "battery" trace.

Happy crunching

[picowatt]

TK,

You have already spent a lot of time and effort on this, and I for one greatly appreciate it. 

But, if I could trouble you for one more measurement:

With the circuit oscillating similarly, please post a scope shot similar to your #490 post timebase and with both vertical channels set as you did for Vbat, but with the scope probes on opposing ends of the load resistor.  I would like to see just how much Vdrop there is at both DC, and more particularly, at AC.  This should provide us with some idea of the battery AC impedance at Fosc.

If you need to get to that "real work", I will understand.

PW

[picowatt]

@PW: Let's go for 100 mA bias current. This keeps it on the Hickok meter, and it makes nicely formed oscillations, and more importantly it gives me a stable and manageable 190-200 mA on the inline DMM which seems to reflect what the load is getting fairly accurately as far as I can tell so far. This produces easily measurable heat and fairly rapid battery depletion with my 5 A-H batteries, and should give manageable run times with NERD's batteries too... ten times longer but still manageable.

So with a fresh 9v, or with a regulated 12 volts input to the Voltage Inverter/Clock, or some other source... it seems that the 10R series resistor is minimum and 50R is a max... maybe I should put a nice wirewound 100R precision pot in there instead of the fixed series resistor.

TK,

I remain a bit puzzled regarding more current measured from Vbatt than is measured at the bias battery.  At DC, they should be the same.  Possibly the assymetrial/distorted AC is being detected in the Ibat measurement and therefore inidicating a higher Ibat.

You might consider finding a convenient way to kill the oscillations like placing a ceramic cap across the gate/source, gate/drain or drain/source.  I am not sure what it will take to stop the oscillations, but you could then measure the currents with the circuit oscillating and then kill the oscillations to get measurements of the DC quiescent conditions.

An alternative would be to place a fairly large cap across the terminals of the Ibat meter to temporarily bypass AC at that meter and see if the indicated current drops to something closer to Ibias.

PW

[TinselKoala]

TK,

Don't waste your time doing the integration. Most of Rosemary's shots are of an averaged (MEAN) p(t) of the product of those two traces. See the attached as a good example.

Just multiply x number of fine points and take the average. If the result is a significant negative number, you're done. In the attached example (same shot from the paper), the MEAN p(t) is -73.4VV.

Also, remember that you are multiplying DC values, not just the relative p-p values. I mention this, even though I know you are aware of this, because your scope shot does not show the zero line for the "battery" trace.

Happy crunching

Actually the scope shot does show the zero trace, it just didn't make it into the crop above.

Here are the actual data points I'll be using for the computation. I've increased the vertical overlay gridlines and used 4 complete cycles. The vertical overlay gridlines have 7.5 lines per screen major division. So the scale becomes as follows: top trace, the CVR, is 2 V/div on the screen so it's 0.267 volts per gridline. The bottom trace, the battery voltage, is at 20 v/div on the screen so it's at 2.67 volts per gridline. The zero marker is shown for the top trace and the 48 volt DC battery level is shown for the bottom trace.