Claimed OU circuit of Rosemary Ainslie

[Harvey]

I'm waiting to hear back from my contact at Tektronix as well.

I'm confident he will state that the Tektronix article does apply to the circuit we are dealing with here, and that everything I have stated is valid.

.99 

Poynt, having read through your post I did not find anything new. Evidently you are mistaken as to my level of expertise in this area.

Here is my challenge to you:
Two differential tests for comparison using the MOSFET Gate rising edge as a trigger in both tests:
TEST 1:
A. Using standard probes with your scope and the reference leads secured at the battery's negative terminal, connect one lead to B(+) and the other lead to the MOSFET drain. Set your scope sweep to read one full cycle on the Mosfet gate for a complete charge/discharge cycle at maximum resolution. Record the data dump for both channels and import it to Excel. Calculate the differential between these two readings.

B. Acquire (since this is quite easy for you as you say) the differential probe of your choice. Place it at the same terminals to perform the same test. Of course here, you will only have a single value to work with, but you must record it and import it to excel. Using the Gate trigger as a synchronizing event, align your data properly for comparison.

Post the results of your analysis

Test 2:
Perform the same test as Test 1 using the CSR instead of the Load Resistor

Post the results of your analysis

Explain why the differential probes do not show any appreciable advantage in this type of research or explain why they do using your collected data as a reference.

[poynt99]

I think I see a problem. That formula is for inches, not millimeters. Is there a check box somewhere that converts it for you? I haven't checked your results yet, but as I recall they are very close to what I derived also.

Which problem?

The web page provides the option for mm or inches. I believe it defaults to mm and that is what I used.

I just tried the web page and it doesn't seem to be loading.

.99

[Harvey]

I think I have solved the problem of the incorrect resistor printing. It is quite appropriate that I post this on this page as the length of the resistor in mm is very close to the page number here. There are two misprints according to my calculations. The length of the resistor and the spacing of the windings. However, the inductance, the number of windings, the resistance and the diameter of the coil work out so perfectly I am convinced that this is the case. The resistor was probably made to imperial measurements with a 1.25" diameter and 10" length. The number of windings results to 48.33 turns with the extra .33 turns being used to secure the wire to the end terminals (0.1674161" beyond the full turn to be exact)

Any thoughts on this?


EDIT: It is possible that the person recording the length measured roughly 250mm and then wrote 150mm

[poynt99]

Poynt, having read through your post I did not find anything new. Evidently you are mistaken as to my level of expertise in this area.

I may be mistaken, but it certainly does not appear that way. Sorry, but that's just the way it is.

Explain why the differential probes do not show any appreciable advantage in this type of research or explain why they do using your collected data as a reference.

It would seem that neither of us at the moment can show actual results to prove this one way or the other (until my diff probes are designed and built), however, I have shown ample substantiation for what I have stated, and I stand by it. There are several other interesting technical quirks that play into this that I have not gone into.

The challenge is moot, the technical write-ups explaining the benefits and in some cases necessity for differential probes are abundant. I have advised what research needs to be done to get over this mental hurdle, but apparently to no avail.

The challenge goes to you to explain why the technical information on this subject is wrong, and there are plenty more that can be cited. I have confidence in what they are saying, as they are probe and oscilloscope manufacturers etc., and furthermore, I have seen the effects and limitations first hand while testing this circuit. What hands-on have you done lately to substantiate the carte blanche dismissal of the necessity of these probes?

I encourage you all once again to do the reading and research, including you Harvey. You would not be making that moot challenge if you were indeed up to speed on the subject, and moreover, you might even be in agreement with me. Do the homework, it's the only way.

.99

[Harvey]

Poynt,

The sole purpose of a differential probe is to provide a real time view (and subsequently a single storable value) of the differential across a given component where all the terminals under test are at a potential that cannot be referenced to ground.

You seem to have some mental hurdle here that prohibits you from seeing that the results are identical in the tests I outlined. I suppose that you have fooled yourself into thinking that the reference wire on each probe is somehow affecting the data in a single probe arrangement thinking that the coaxial shielding on the differential probes would not do the exact same thing. The fact of the matter is that the single ended coaxial shielding is more susceptible to influence and demands a very good CMRR on the two inputs to account for it.

Differential Probes have their place, but they are not needed in this analysis, nor would they offer any real advantage at the data collection level. To say that they would be more accurate is the same as saying the single probes are not accurate, and nothing could be farther from the truth.

Looking forward to the results of your home-made differential probe kit - too bad it will not be usable in any scientific paper without first having it properly calibrated and documented by NIST or the like.