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Saturday, February 26, 2011

77 - which value is right?

Dear Reader,

I have a problem which I'm hoping will be addressed. It's this. Energy measurement is based on the product of voltage and amperage over time. And energy is measured in Joules which, in turn, is based on wattage which, as mentioned, is vi*dt.

Now. We've been the happy recipient of the use of some really zut DSO's. The one gives us data dumps in the half million and the other in the million sample range. Hugely detailed. Each sample range under observation is really thoroughly accounted. And the dumps are right out of the moment that the sample was captured. How the different DSO's measure their mean averages, or anything else, depends on that initial sample capture. It's that dump that represents an actual record. And we can access that record of samples - right out of the DSO.

Typically on the multiple channels that these instruments provide - it's possible to measure the different points on each circuit. So it is that the battery voltage and the shunt voltage are shown simultaneously. Therefore is it possible to measure them both - to estabish vi - in real time. As they occurred. So. One can take a record of that sample range and then transpose it to the spreadsheet for analysis and do a moment by moment computation of those measurements. For example, one can take the voltage across the shunt, divide it by the resistive value of the shunt and get the instantaneous current measurement. Then one can multiply that current by the measured voltage and that will give the actual measure of that instantaneous sample as it happens, so to speak. And one can do that sum for each of those 500 000, or 1 million samples - as required.

Alternatively, one can take the sum of all those voltages over that entire sample range and divide it by the number of samples to get a mean average of the current flow and a mean average of the applied source voltage and one will then get the average of the amount of energy applied over that time period related to the sample range.

Here's the kicker. The sum of the instantaneous wattage computed against each sample is never the same as the mean average. Those numbers never relate to each other.

I do have an answer - but I'm not sure if it's classical. Poynty, - if you're reading here - or anyone. I'd be glad of some kind of explanation. Which of those two systems is right? Certainly they're NEVER in agreement with each other.

Why this is relevant is because the math trace is the instantaneous product of both the shunt and the battery voltage. At higher wattage outputs the mean average of the shunt voltage defaults to positive but not that instantaneous product - not that math's trace. This remains negative. Interestingly - possibly because of the higher voltages, the battery voltage first dips by a half a volt or thereby and then steadily climbs back to its previous value.

It's puzzling.

Kindest regards,
Rosemary

76 - on negative triggering and its implications

Dear Reader,

This is a very generalised description of the negative triggering and it's results on the waveform that is proposed to be demonstrated.

It is established that current moves through conductive and inductive material. Above zero voltage induces a clockwise directional flow and below zero, conversely, induces an anti-clockwise flow. The direction of current flow then induces a voltage across circuit material that is established in counterphase to that applied voltage.

From a detailed analysis of the data taken from our two digital storage oscilloscopes it is evident that the amount of voltage applied to the element/resistor - from the battery and during that brief 'on' period - is consistent with the amount of wattage that is measured to be dissipated as heat at the resistor.

But it is also evident that the current resulting from that applied voltage did not flow to the negative terminal of the battery as there would be some corresponding evidence of an applied above zero voltage at the shunt resistor. It is proposed that because the gate signal immediately defaults to zero the passage of this current flow is interrupted that it cannot flow through the circuit path to reach the negative terminal of the supply. Again. The time during which the circuit is closed, to enable this flow, is brief. And the resistance from the circuit is sufficient to prevent a 'through flow' of that current.

The voltage applied to the resistor, albeit small, is now in antiphase to the source voltage. And it is consistent with the amount of voltage applied during that brief 'on' period enabled by the duty cycle. The voltage across the element then discharges that small negative voltage through the closed circuit path, through the battery, then through the Zener body diode of the MOSFET and back to the source of that negative voltage being the element/resistor. This results in a discharge of that voltage at the resistor. It is also consistent with a small negative voltage spike measured at the shunt.

But in moving through the circuit that anti-clockwise current flow has increased the battery voltage and it has simultaneously established an opposite positive voltage in the conductive/inductive properties of the circuit material. This postive voltage now has no restriction to enable a current flow path from the circuit as the signal at the gate is now negative. And negative charge signal at the gate of the MOSFET will not repel a postive charge. The source battery voltage is now marginally higher as a result of that brief anti-clockwise current flow. And it is then able to discharge a marginally greater current flow. This combines with the discharge of positive voltage from the circuit material all of it moving as current flow in a clockwise direction. And this, in turn, establishes a marginally greater current flow and a marginally greater negative voltage is again establshed on the circuit components. This then discharges that voltage as current flow in an anti-clockwise. This then again increases the level of voltage in the battery. And so it goes, ramping up to higher and higher voltages in a resonating condition. Until the level of voltage in that resonating condition exactly equals the limit to the amount of voltage induced in those circuit components. At that point it reaches the limit in the level of it's resonance. Then the switch defaults to present an brief closed condition to the supply. And so the cycle is repeated.

In effect, the osciallations that result from the negative triggering are the result of - and limited to - the sum of the voltages induced from the circuit material and not from the source. In the discharge of that voltage there is a resulting conservation of charge at the initial supply source.

What may be proved by this is that potential difference can be transferred to passive circuit components that they, in turn, can become an energy supply source. Certainly the fact that the battery voltage is in antiphase to the voltage measured across the shunt - is indicative of this. As the only way that this antiphase voltage condition across the shunt and the supply, can otherwise be generated is with the application of an alternative energy supply source to the circuit.

There are subtleties in that resonating condition that need fuller explanation. But I think it is outside the scope of this explanation. There are also certain questions that relate to closed circuit conditions that are not here fully explored. These will be partially covered in that report that will result from that demonstration.

Hope that helped.
Kindest regards,
Rosemary