GM East Burst Heater Circuit

[MarkE]

If reliable measurements of temperature that yield heating power are actually desired, a brief literature search will reveal how it is generally done. The same load should be used for both the control and experimental trials. The imperfectly insulated load will of course take some time to reach its equilibrium temperature with the surroundings; at this point it will be dissipating the same amount of power it is receiving from the supply. (Or from wherever it is getting its power, like its zipons being agitated or whatever.) The temperature-time curves are plotted for both DC supply from a voltage regulated supply, and the Burst Heater circuit. The power supplied in each condition can be measured as DC power in, and the power dissipated at the load can be determined by finding the equilibrium temperature and comparing it to that obtained at the various non-extraordinary DC power levels used for calibration. This might take some time, as in a good load cell it might take 30 minutes or more for it to reach equilibrium temperature. The load's thermal mass and insulation should be chosen so this thermal settling time is not too long and not too short, and of course the load must be allowed to cool back to (regulated, constant) ambient temperature before beginning each trial run. Several trials should be made at each DC power level to allow for statistical accuracy checks. If variations are made in the operating parameters of the Burst Heater circuit, several trials should be performed at each set of parameters as well. The same load cell should be used because small differences that may not be under the experimenter's control could affect results if different load cells are used. A schedule of trials can and should be prepared beforehand and the order of trials can be randomized so that load cell ageing effects, if they occur, can be distributed evenly or randomly over the data set. Automated data logging, or at least a chart recorder record of time and temperature, would be a big help, but it is actually possible for a determined individual to record the necessary datapoints with paper and pencil.
This process will yield a series of curves in temperature-time plots. The equilibrium temperature reached by the Burst Heater trials can be compared to the temperatures reached at the various DC power levels and interpolated to yield the actual power dissipation level of the load cell when it is powered by the Burst Heater circuit.
Presumably the conventional power input to the Burst Heater circuit can be accurately measured... it could be powered by the same DC power supply at the same power levels as used for the DC calibrations, for example.
This process will also yield the data necessary for actual input and output energy comparisons as well, if anyone cares to do a bit more math.

I think that the process can be somewhat compressed by the fact that there are some interesting data points:

A. Pulse circuit test.  Let rise until the temperature stabilizes for at least five thermal time constants.  The thermal time constant can be estimated once there are at least three data points, and the rate of temperature rise has declined to half or less the starting rate of rise.

B. Cool off.  Turn off power.  Open vessel and let cool off until the temperature in the vessel is within 2C of ambient.

C. DC tests.
1) The average current of 112mA. (assumes duty cycle and average currents measurements taken of the pulse circuit operation are reasonably accurate)
2) The rms equivalent current of 229mA, (assumes duty cycle and average currents measurements taken of the pulse circuit operation are reasonably accurate)
3) The rms equivalent of 128% power vs:   = 229mA*(1.28)^0.5 = 259mA
4) The presently measured 363mA current

D. same as B

E-G, repeat A, B, and C.


The thermal time constant of the heat exchanger can be determined using the first pulse test.  Once the thermal time constant is known then the option exists to either cool off between DC runs, or simply adjust to progressively higher settings and wait five or more time constants between recording the results for each power step for the rise over ambient to stabilize.  It doesn't provide quite as much data, but unless the power inputs vary massively, and they don't, or the power leak rate is more than a small fraction of power in, then there isn't a lot of new useful data to be had by cooling down and then restarting during runs of like types, IE DC versus pulsed.  I do think that the unit should cool off between the DC runs and the pulse runs. 

I would do the pulse run first.  Then the DC runs can be stopped when a data point is found that exceeds the temperature rise of the pulse circuit.  In the unlikely case that the pulse circuit temperature rise is not even as high as the average current case, then a new lower current data point will be needed. 

[MarkE]

Greg, I hear that you say that I gave up on you.  I have suggested some tests that I recommend you do before spending a ton of time and money building a giant capacitor bank.  The last you wrote, you were not interested in my suggestions.  The tests are directed at comparing the heat that you can evolve from your resistor when driving it at different DC current levels compared to the pulse drive.  The theory is simple enough:  When a resistor is driven by a rectangular pulse train (resistance translates voltage and current so we can refer to either), the energy imparted by each pulse is:

V²/R*T_ON or alternately: I²*R*T_ON

To get average power we just divide by: T_PERIOD.

The equivalent DC voltage or current is then: 

V_rms = V*(T_ON/T_PERIOD)^0.5
V_rms = V_ave*(T_PERIOD/T_TON)^0.5

I_rms = I*(T_ON/T_PERIOD)^0.5
I_rms = I_ave*(T_PERIOD/T_TON)^0.5

Whether you believe it or not, DMMs really do a very good job of measuring V_ave, and I_ave even with spiky signals.  So, FWIW you can measure that directly.  Average voltage and/or current is really only useful when one or the other, voltage or current are stable.  Then if they are both measured at the power source the product does come out close to average power.  But remember, one or the other has to be stable.  In your situation, the supply voltage can be made very stable with decoupling capacitors.

Rms values require integration.  For a clean rectangular pulse the equations above represent the appropriate integrals.  If there is any issue keeping the voltage steady during the pulse, decoupling capacitors close in to the switching transistor will fix that problem.  If you are using a flyback / freewheeling diode, you want to make the battery power connection right at the cathode of the diode / capacitor connection, and keep the: MOSFET, flyback diode, capacitor wiring loop as small as possible, and make the battery negative connection right at the MOSFET source.  You can then run a wire from the diode/capacitor battery + connection off to the positive side of the heater resistor, and a wire from the MOSFET drain to the heater resistor.  You would probe with your scope from the MOSFET source to the MOSFET drain with one channel and from the MOSFET source to the diode/capacitor connection with the other.  If you use 75 Ohm resistors in series with the probe tips you will get pretty clean and accurate measurements.  The voltage across your load is the difference voltage between the two channels.

What good old ordinary circuit theory predicts is that the DC rms equivalent drive will evolve the same amount of heat from the resistor as the pulse drive.  If you see 25% more with the pulses than their rms equivalent, then something unexpected is going on that has never been seen by people who design switching power circuitry when they take careful measurements.  If you cross that bar while showing that there are no obvious errors in the measurements, and the technique I have explained should ensure that you don't have such errors then you will get a lot of attention.  If what you have so far is actually an illusion, then these tests will show you that.

Do what you want.  I know you don't trust me.  But these tests really are valid and will tell you and anyone else who reviews them and the results whether or not you have found an anomaly for a lot less effort and cost than the capacitor bank you said you were assembling.

[TinselKoala]

 GMeast said,

I'm pretty sure he figured he was in a losing argument in that he would have to call me a liar or accuse me of falsifying data, and that's a serious thing to try ... even for them.

I find it hugely ironic.... and ROFL funny.... that Gmeast makes such a statement, on the forum of the proven liar and fabricator of data Rosemary Ainslie. Ainslie still has the fake Figure 3 scopeshot displayed prominently in her "unretracted" daft manuscripts and her "adden-dumb" still claims it is valid. She has never issued any statement of correction or explanation for the Figure 3 scopeshot, and _all of her claims_ involving heat and "no measurable power from the supply"  depend on that shot and the other, similar, fabricated scopeshots which show ample Gate drive voltages during the non-oscillating portions but have _no_ current shown.

And let's not forget this Little demonstration of when she actually made Donovan Martin lie for her, in the video she posted to one of her four YouTube accounts, and then later shouted that "she did not post that video".

http://www.youtube.com/watch?v=neME1s-lEZE

The further strings of lies from Ainslie can be seen in practically every post she makes, like her present accusations that I "rely" on DMM readings, when it is clear to everyone with eyes and a brain that I RELY on digital oscilloscope readings and spreadsheet calculations and only use the DMM readings as PROOF that the experiment is occurring as I say.

GMeast is not doing his own credibility any good by associating himself with the proven liar and data fabricator Rosemary Ainslie.

[MarkE]

GMeast said,
I find it hugely ironic.... and ROFL funny.... that Gmeast makes such a statement, on the forum of the proven liar and fabricator of data Rosemary Ainslie. Ainslie still has the fake Figure 3 scopeshot displayed prominently in her "unretracted" daft manuscripts and her "adden-dumb" still claims it is valid. She has never issued any statement of correction or explanation for the Figure 3 scopeshot, and _all of her claims_ involving heat and "no measurable power from the supply"  depend on that shot and the other, similar, fabricated scopeshots which show ample Gate drive voltages during the non-oscillating portions but have _no_ current shown.

And let's not forget this Little demonstration of when she actually made Donovan Martin lie for her, in the video she posted to one of her four YouTube accounts, and then later shouted that "she did not post that video".

http://www.youtube.com/watch?v=neME1s-lEZE

The further strings of lies from Ainslie can be seen in practically every post she makes, like her present accusations that I "rely" on DMM readings, when it is clear to everyone with eyes and a brain that I RELY on digital oscilloscope readings and spreadsheet calculations and only use the DMM readings as PROOF that the experiment is occurring as I say.

GMeast is not doing his own credibility any good by associating himself with the proven liar and data fabricator Rosemary Ainslie.

I don't visit the sins of the Tasmanian devil on the follower.  Her crazy behavior does not reflect directly on him.  I believe that Greg really believes that he's getting a 25% surplus.  So the task is to find out whether or not he is right.  I think that he has gone to some effort to try and conduct valid tests.  I hope that he will follow through one way or another.  I offer my suggestions as one way of following through with less expense and effort than what I understand he has proposed with the big capacitor bank.  If he takes up my suggestions, great.  If he doesn't, but follows through by some other means, that is good too.