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#260 by ThinkerX on 17 Dec, 2015 07:41
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This has been discussed before. Using several hundred Watts does not make the thermal response any less significant. It appears that at every power level thermal effects are greater than any indication of thrust. In the absence of any information from Yang or Shawyer that could be used to replicate their apparatus and independently confirm their results, the best that can be done is to build something close and test it. If this em-drive force does exist it would eventually be seen by some other experimenter even without knowing exactly what Shawyer or Yang did. Science has been down this path before. If the phenomena cannot be demonstrated, it doesn't exist.
Hence my proposal: a set of standardized experiments to be performed, if possible by the DIY types. -
#261 by ZhixianLin on 17 Dec, 2015 08:28
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Hey, why not try my design. I think it is easier to understand.
Here it is:
http://forum.nasaspaceflight.com/index.php?topic=38996.0 -
#262 by Rodal on 17 Dec, 2015 11:49
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An update on our 100kW test project. Model using HFSS using eigenmode solver, TE013 mode 914.85MHz Q=133526. Loop coupled design for ease of build, cost and stress concerns.
As we are planning to use a high power coax line and are designing as a pressure vessel, one recommendation is to use copper cladded stainless steel... does anyone see any objections to the use of this material so long as we clad the internals with copper? This would help us with vessel integrity and cooling; while I do think we will achieve resonance is there any EM-Drive Q thruster theories that say not to do this (i.e. impacting the quantum vacuum??).
It is noteworthy to remark that this is the ONLY test by anyone (as far as I know) where there is a deliberate attempt to test for anomalous thrust forces that are way beyond the forces produced by thermal effects.
Assuming the frustum is resonating with 100KW input, won't we see 100KW of heat generated by the furstum? If we see 100W heat only, we can only assume that 99.9% power are reflected back and this test is no better than a 100W test.
...
This is a good long game plan, but as an observer on the sidelines, it seems to me that the best approach would be to first work out just what is required to reproduce thrust at the levels claimed by Shawyer and Yang. Since everyone including Eagleworks is really starting from scratch, neither Shawyer or Yang provide enough detail to reproduce their frustums and microwave sources, having an idea how to deal with the systemic and heat related issues is good, but it is a waste of time and money until you have a decent frustum that does produce enough thrust that it is even possible to try and rule out noise.
As a separate issue, it really seems from what limited information I have gone through at present, that until someone is able to scale up the delivered power to several hundred watts resononating, you may not get the kind of thrust in either of the earlier claims.
Basically I guess what I am saying is that because the DIYs are working in atmosphere and with limited resources, it will require a thrust in at least tens of mNs before any practical elimination of thermal and systemic effects will be practical.
This has been discussed before. Using several hundred Watts does not make the thermal response any less significant. It appears that at every power level thermal effects are greater than any indication of thrust. In the absence of any information from Yang or Shawyer that could be used to replicate their apparatus and independently confirm their results, the best that can be done is to build something close and test it. If this em-drive force does exist it would eventually be seen by some other experimenter even without knowing exactly what Shawyer or Yang did. Science has been down this path before. If the phenomena cannot be demonstrated, it doesn't exist.
It should not be assumed that the thermal effects will scale linearly with input power, on the contrary:
1) While Maxwell's equations are linear, the Navier Stokes equations of fluid dynamics governing thermal natural convection (lift and drag effect due to air heating) are nonlinear. The tendency of the naturally convective thermal system towards turbulence relies on the Grashof number, which goes like the cube of the characteristic length and the inverse of the square of the kinematic viscosity. It can be thought of as Reynolds number with the velocity of natural convection replacing the velocity in Reynolds number's formula. Natural convection is highly dependent on the geometry of the hot surface, a general correlation that applies for a variety of geometries shows the Nusselt number to be a nonlinear function of the Prandtl number and a nonlinear function of the Reynolds number.
2) The experimental results of Prof. Yang showed strong nonlinearity between the measured force and the input power (see attached chart). Prof. Yang's experiments show diminishing returns (actually slight decrease in measured forces for input power exceeding 300 Watts and general flat response) for increasing input power.
Hence it does not follow that the thermal artifacts will scale linearly in experiments conducted at much higher input power. On the contrary, Prof. Yang's experimental results show strong nonlinearity, with the touted "EM Drive" force dependence on input power effectively dissappearing after about 300 watts, the dependence looks practically flat at input powers greater than 300 W. The nonlinearity of the "force" vs. input power experimental relation of Prof. Yang has not yet been scientifically modeled hence its nature can only be speculated until a verifiable model is demonstrated.
This shows that if anything, experiments conducted at ambient conditions with low power may be highly misleading and NOT linearly scalable to higher powers, just as it would be highly misleading to conflate the flight of an insect with the flight of an airplane (the aerodynamics are completely different at very low Reynolds numbers).(The range of Reynolds number in insect flight is about 10 to 10^4, which lies in between the two limits that are convenient for theories that try to simplify the nonlinearity of Navier Stokes fluid dynamics: inviscid steady flows around an airplane's airfoil and Stokes flow experienced by a swimming bacterium. For this reason, this intermediate Reynolds number range used by insects in their flight is not as well understood as the high Reynolds number regime for airplanes. )
Before the Wright Brothers flying machine, there were lots of experimenters trying to make flying machines fly similarly to the way insects or small birds fly. Those experiments resulted in utter failure.
Instead of trying to model the flight of an insect, the Wright Brothers built their own wind tunnel and addressed the problems associated with flight of machines that could carry people rather than insects. In that sense, the Wright Brothers understood that the Navier-Stokes equations describing fluid dynamics are nonlinear equations.
Of course, the best way to eliminate this pesky influence of the surrounding air is to conduct the tests in a vacuum chamber, as done by Tajmar at TU Dresden and NASA Eagleworks, which resulted in measured "EM Drive forces" that are orders of magnitude smaller than the forces claimed by Shawyer and Yang in their experiments (all of them conducted in air).
It is very noteworthy that neither Yang nor Shawyer have reported a single EM Drive experiment in vacuum. Instead of asking Boeing whether they are still working with Shawyer, (which we know from both Boeing and Shawyer, no longer working with each other), I would ask Boeing what were Boeing results of the EM Drive tests in vacuum, as the Boeing/Shawyer arrangement was supposed to eventually lead to testing of a satellite in the vacuum of space, and Boeing had ready availability of vacuum chambers to conduct such a test
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#263 by Tellmeagain on 17 Dec, 2015 12:33
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Any announcement that EW is going to Glenn would be wildly major news IMHO because it has to mean that they've seen thrust levels above the noise floor that the Glenn equipment requires before testing there, and also the thrust isn't already attributable to anomalous thrust.
The lack of publishing from Yang may be because she's discovered that her reported thrust was anomalous as she tightens up her testing methods. Or not.
I think your understanding of "anomalous thrust" is different from the majority of people here. Only those that can not be explained by existing physics are anomalous. -
#264 by Tellmeagain on 17 Dec, 2015 12:40
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The last institutional published experimental report was by Tajmar at the Technische Universität Dresden in Germany.
We are waiting to hear news from NASA regarding:
1) Publication of NASA's Eagleworks EM Drive tests performed in vacuum, including discussion/analysis of thermal expansion effects and effects from forces resulting from the magnetic damper.
2) Confirmation of whether or not a new testing campaign will commence at NASA Glenn to replicate the tests at NASA Johnson (Eagleworks), and if so when are the NASA Glenn results expected to be announced/reported.
Remarkably, Yang (in China) has not published any new results for a considerable amount of time, and her last publication dealt with the considerable thermal effects on her experiments (her paper on temperature vs. time measurements throughout a heated EM Drive using embedded thermocouples).
Concerning Do-It-Yourself experiments, the last experimental report was by RFMWGUY. We are waiting to hear from Shell on her meticulously and thoroughly designed testing program.
The abstract deadline for 52nd AIAA/SAE/ASEE Joint Propulsion Conference http://www.aiaa-propulsionenergy.org/JPC/ is Jan 12th, 2016. Hurry up NASA!
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#265 by glennfish on 17 Dec, 2015 12:42
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I have a small thermal plume from the frustum but the heated pressure diff (balloon effect) is vented out and down the air line.
Shell
Shell,
I'm following you, but perhaps I'm not explaining myself. I see three thermal effects.
1. Air venting from the frustum, which you're managing
2. Air density within the frustum, which cannot be vented. Hot air is lighter than cold air at the same pressure (no venting changes that)
3. The conical exterior wall heating will set up different air flow rates between the narrow and wide ends, effects dependent upon frustum orientation.
I don't know how to design out the latter two.
I just want to be sure I understand your constraints.
if I'm right, it doesn't matter, provided you incorporate those effects into your test protocol. I'm pretty convinced that any thrust greater than zero can be observed statistically with the right protocol even if these effects aren't compensated for in the physical design.
Just want to be sure I understand what you can and can't do, have and haven't done. Once you start grabbing data, I expect to be tossing test methods over the wall like a whirling dervish. Having a list of what's not compensated for leads to tests to characterize those items, which makes anomalous effects easier to see. -
#266 by Rodal on 17 Dec, 2015 12:51
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I have a small thermal plume from the frustum but the heated pressure diff (balloon effect) is vented out and down the air line.
Shell
Shell,
I'm following you, but perhaps I'm not explaining myself. I see three thermal effects.
1. Air venting from the frustum, which you're managing
2. Air density within the frustum, which cannot be vented. Hot air is lighter than cold air at the same pressure (no venting changes that)
3. The conical exterior wall heating will set up different air flow rates between the narrow and wide ends, effects dependent upon frustum orientation.
I don't know how to design out the latter two.
I just want to be sure I understand your constraints.
if I'm right, it doesn't matter, provided you incorporate those effects into your test protocol. I'm pretty convinced that any thrust greater than zero can be observed statistically with the right protocol even if these effects aren't compensated for in the physical design.
Just want to be sure I understand what you can and can't do, have and haven't done. Once you start grabbing data, I expect to be tossing test methods over the wall like a whirling dervish. Having a list of what's not compensated for leads to tests to characterize those items, which makes anomalous effects easier to see.
Statistical correlation does not imply causation. This is particularly so when the sample size of the statistical population is so small as in RFMWGUY's experiments. The results of the statistical tests may just be governed and explained by classical physics, as per transient thermal convection lift and drag effects of the heated magnetron in RFMWGUY's experiment. Therefore mathematical physics analysis cannot be substituted by statistical analysis and your point is well taken that these issues need to be analyzed with mathematical physics. -
#267 by OnlyMe on 17 Dec, 2015 13:04
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.....
Basically I guess what I am saying is that because the DIYs are working in atmosphere and with limited resources, it will require a thrust in at least tens of mNs before any practical elimination of thermal and systemic effects will be practical.
This has been discussed before. Using several hundred Watts does not make the thermal response any less significant. It appears that at every power level thermal effects are greater than any indication of thrust. In the absence of any information from Yang or Shawyer that could be used to replicate their apparatus and independently confirm their results, the best that can be done is to build something close and test it. If this em-drive force does exist it would eventually be seen by some other experimenter even without knowing exactly what Shawyer or Yang did. Science has been down this path before. If the phenomena cannot be demonstrated, it doesn't exist.
I believe that was essentially my point. Build a frustum/microwave source that generates a thrust sufficient, that it is even practical to try and start eliminating.... Spending too much time and money to eliminate systemic and thermal effects before you have a system that generates enough thrust to work with, does not seem a good use of resources.
With unlimited funding and/or a vacuum chamber, chasing the noise before you have demonstrated thrust is wasteful. It would be different if you were duplicating something Shawyer or Yang already constructed, but if that were possible you would not see everyone, starting out with different system designs. -
#268 by rfmwguy on 17 Dec, 2015 13:19
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We have 2 approaches for thermal mitigation; statistical and mathematical physics. I think this is excellent. Statistical is more straight forward, but the latter is not. We have several possible ways to look at the latter and I have heard fluid dynamics proposed, but I don't see a way mere mortals (DIYers) can do this.
(...) Therefore mathematical physics analysis cannot be substituted by statistical analysis and your point is well taken that these issues need to be analyzed with mathematical physics.I have a small thermal plume from the frustum but the heated pressure diff (balloon effect) is vented out and down the air line.
Shell
(...)Just want to be sure I understand what you can and can't do, have and haven't done. Once you start grabbing data, I expect to be tossing test methods over the wall like a whirling dervish. Having a list of what's not compensated for leads to tests to characterize those items, which makes anomalous effects easier to see.
So, I propose if statistical AND the latter are going to be required moving forward for ambient air testing, we need a concensus and a pathway with specifics. Anything you brain trusts can do to set up standards, I propose that Shell tries these out (sorry, pal)...or wait for me sometime in June of next year. The sooner the better IMHO.
If fluid dynamics modeling is out of the picture, what is possible? -
#269 by glennfish on 17 Dec, 2015 13:20
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Statistical correlation does not imply causation. This is particularly so when the sample size of the statistical population is small, as in RFMWGUY's experiments. The results of the statistical tests may just be governed and explained by classical physics, as per transient thermal convection lift and drag effects of the heated magnetron. Therefore mathematical physics analysis cannot be substituted by statistical analysis and your point is well taken that these issues need to be analyzed with mathematical physics.
Absolutely agree.
From my point of view, there is a universe of noise sources that has to be characterized.
There may be a signal in the noise.
If the noise is understood, then we can set up a trials methodology that will indicate signal if the signal is > than some threshold. The # of trials to achieve statistical significance depends on the amplitude of the noise, the amplitude of the signal, the random variations in both and a list of other things that need to be itemized.
Attached is a simulation I provided Shell earlier of how visible a signal would be under various constraints. For now, I want to be sure I understand her constraints so the simulation can be adapted accordingly, which will lead to a trials methodology. Cells in yellow can be changed to suit various assumptions.
Right now, it looks like the simulation is missing some factors for consideration, hence my questions to her.
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#270 by OnlyMe on 17 Dec, 2015 13:22
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I have a small thermal plume from the frustum but the heated pressure diff (balloon effect) is vented out and down the air line.
Shell
Shell,
I'm following you, but perhaps I'm not explaining myself. I see three thermal effects.
1. Air venting from the frustum, which you're managing
2. Air density within the frustum, which cannot be vented. Hot air is lighter than cold air at the same pressure (no venting changes that)
3. The conical exterior wall heating will set up different air flow rates between the narrow and wide ends, effects dependent upon frustum orientation.
I don't know how to design out the latter two.
I just want to be sure I understand your constraints.
if I'm right, it doesn't matter, provided you incorporate those effects into your test protocol. I'm pretty convinced that any thrust greater than zero can be observed statistically with the right protocol even if these effects aren't compensated for in the physical design.
Just want to be sure I understand what you can and can't do, have and haven't done. Once you start grabbing data, I expect to be tossing test methods over the wall like a whirling dervish. Having a list of what's not compensated for leads to tests to characterize those items, which makes anomalous effects easier to see.
Statistical correlation does not imply causation. This is particularly so when the sample size of the statistical population is small, as in RFMWGUY's experiments. The results of the statistical tests may just be governed and explained by classical physics, as per transient thermal convection lift and drag effects of the heated magnetron. Therefore mathematical physics analysis cannot be substituted by statistical analysis and your point is well taken that these issues need to be analyzed with mathematical physics.
The portion in my bold emphasis above is just what I was referring too. If you don't have enough anomalous thrust to work with.., or a vacuum chanmber.., you don't have enough to work with.
There have been some good ideas on just how some of the thermal effect might be handled. Most of the time they would require additional engineering, which requires funding.., and may introduce other systemic issues.
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#271 by OnlyMe on 17 Dec, 2015 13:34
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We have 2 approaches for thermal mitigation; statistical and mathematical physics. I think this is excellent. Statistical is more straight forward, but the latter is not. We have several possible ways to look at the latter and I have heard fluid dynamics proposed, but I don't see a way mere mortals (DIYers) can do this.
(...) Therefore mathematical physics analysis cannot be substituted by statistical analysis and your point is well taken that these issues need to be analyzed with mathematical physics.I have a small thermal plume from the frustum but the heated pressure diff (balloon effect) is vented out and down the air line.
Shell
(...)Just want to be sure I understand what you can and can't do, have and haven't done. Once you start grabbing data, I expect to be tossing test methods over the wall like a whirling dervish. Having a list of what's not compensated for leads to tests to characterize those items, which makes anomalous effects easier to see.
So, I propose if statistical AND the latter are going to be required moving forward for ambient air testing, we need a concensus and a pathway with specifics. Anything you brain trusts can do to set up standards, I propose that Shell tries these out (sorry, pal)...or wait for me sometime in June of next year. The sooner the better IMHO.
If fluid dynamics modeling is out of the picture, what is possible?
Didn't Tajmar put the frustum in a box filled with fiberglass to reduce or eliminate thermal convection effects? That should be doable with Shell's design.., if she has enough raw thrust to make it worth the effort.
Another approach, potentially possible with a fully sealed frustum, might be to evacuate the frustum itself. As long as the frustum is ridged enough in design, that should eliminate or at least significantly reduce ballooning... And might be possible with a less expensive vacuum pump than required for a vacuum chamber.
There are many things that might be possible for a DIY experiment.., IF the thrust seen is enough to warrant the investment in additional time and money. -
#272 by Rodal on 17 Dec, 2015 13:41
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Yes, but when Tajmar performed the experiments in vacuum he measured much smaller forces, therefore this showed that the box did not solve the thermal artifacts caused by air.
We have 2 approaches for thermal mitigation; statistical and mathematical physics. I think this is excellent. Statistical is more straight forward, but the latter is not. We have several possible ways to look at the latter and I have heard fluid dynamics proposed, but I don't see a way mere mortals (DIYers) can do this.
(...) Therefore mathematical physics analysis cannot be substituted by statistical analysis and your point is well taken that these issues need to be analyzed with mathematical physics.I have a small thermal plume from the frustum but the heated pressure diff (balloon effect) is vented out and down the air line.
Shell
(...)Just want to be sure I understand what you can and can't do, have and haven't done. Once you start grabbing data, I expect to be tossing test methods over the wall like a whirling dervish. Having a list of what's not compensated for leads to tests to characterize those items, which makes anomalous effects easier to see.
So, I propose if statistical AND the latter are going to be required moving forward for ambient air testing, we need a concensus and a pathway with specifics. Anything you brain trusts can do to set up standards, I propose that Shell tries these out (sorry, pal)...or wait for me sometime in June of next year. The sooner the better IMHO.
If fluid dynamics modeling is out of the picture, what is possible?
Didn't Tajmar put the frustum in a box filled with fiberglass to reduce or eliminate thermal convection effects? That should be doable with Shell's design.., if she has enough raw thrust to make it worth the effort.
Another approach, potentially possible with a fully sealed frustum, might be to evacuate the frustum itself. As long as the frustum is ridged enough in design, that should eliminate or at least significantly reduce ballooning... And might be possible with a less expensive vacuum pump than required for a vacuum chamber.
There are many things that might be possible for a DIY experiment.., IF the thrust seen is enough to warrant the investment in additional time and money.
As usual with all these experimenters, Tajmar did NOT conduct a Computational Fluid Dynamics simulation, so the "box" concept was not scientifically analyzed, and his vacuum experiments showed the "box" to not have effectively addressed the air convection effects.
Such "solutions" as the "box" are based on intuition rather than analysis. Hence it is not too surprising that actual experiments show them to be ineffective. -
#273 by rfmwguy on 17 Dec, 2015 13:55
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OK, here's something from left field...a visualization of fluid dynamics, or:
https://en.wikipedia.org/wiki/Schlieren_photography
Lets say we video a static frustum using Schlieren lenses, get a proper scale reference, temperature, humidity and plume velocity...could we effectively predict thermal-dynamic forces? -
#274 by Rodal on 17 Dec, 2015 14:12
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OK, here's something from left field...a visualization of fluid dynamics, or:
Not enough for a quantitative prediction (it would not eliminate the need for a Computational Fluid Dynamics simulation), but it would elucidate what is going on more than present experiments conducted in air based on intuition rather than fluid dynamics analysis:
https://en.wikipedia.org/wiki/Schlieren_photography
Lets say we video a static frustum using Schlieren lenses, get a proper scale reference, temperature, humidity and plume velocity...could we effectively predict thermal-dynamic forces?
It would be particularly useful if it could be accurately monitored with accurate clock timing (or some other means to show the magnetron going ON and OFF in the Schlieren movie) to show what happens for example, whenever the magnetron is turned ON and OFF (rather than assuming without computational fluid dynamics analysis that turning the magnetron on will result in lift rather than drag under an existing thermal lift force) -
#275 by rfmwguy on 17 Dec, 2015 14:17
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I can do this, but it is a moderate cost to get the 2 lenses. I'd prefer not doing it if there is no quantitative value. IOW, it might be nice to see, but if it cannot be used as a predictor for thermodynamic movement, not sure the expense is warranted. This is what stopped me from doing this recently...I could not justify the expense if it wouldn't contribute to the dataset...if that makes sense...OK, here's something from left field...a visualization of fluid dynamics, or:
Not enough for a quantitative prediction, but it would elucidate what is going on more than present experiments
https://en.wikipedia.org/wiki/Schlieren_photography
Lets say we video a static frustum using Schlieren lenses, get a proper scale reference, temperature, humidity and plume velocity...could we effectively predict thermal-dynamic forces?
It would be particularly useful if it could be accurately monitored with accurate clock timing to show what happens for example, whenever the magnetron is turned ON and OFF (rather than assuming without analysis that turning the magnetron on will result in lift rather than drag under an existing thermal lift force) -
#276 by Rodal on 17 Dec, 2015 14:19
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I can do this, but it is a moderate cost to get the 2 lenses. I'd prefer not doing it if there is no quantitative value. IOW, it might be nice to see, but if it cannot be used as a predictor for thermodynamic movement, not sure the expense is warranted. This is what stopped me from doing this recently...I could not justify the expense if it wouldn't contribute to the dataset...if that makes sense...OK, here's something from left field...a visualization of fluid dynamics, or:
Not enough for a quantitative prediction, but it would elucidate what is going on more than present experiments
https://en.wikipedia.org/wiki/Schlieren_photography
Lets say we video a static frustum using Schlieren lenses, get a proper scale reference, temperature, humidity and plume velocity...could we effectively predict thermal-dynamic forces?
It would be particularly useful if it could be accurately monitored with accurate clock timing to show what happens for example, whenever the magnetron is turned ON and OFF (rather than assuming without analysis that turning the magnetron on will result in lift rather than drag under an existing thermal lift force)
Would you be able to accurately tie what is shown in the Schlieren movie to the actual timing of the turning ON and OFF of the magnetron ? -
#277 by rfmwguy on 17 Dec, 2015 14:27
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Doc,
Yes, a video would both have a timer and contain audio to denote mag on (xformer hum).
Also, I could embed a spectrum analyzer display in the corner to show freq locking, which would probably be a better indication of start.
Plume temp would be hard to measure with my IR thermometer...can get a case temp or sync a thermal vid. -
#278 by Rodal on 17 Dec, 2015 14:29
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Doc,
Yes, a video would both have a timer and contain audio to denote mag on (xformer hum).
Also, I could imbed a spectrum analyzer display in the corner to show freq locking, which would probably be a better indication of start.
Plume temp would be hard to measure with my IR thermometer...can get a case temp or sync a thermal vid.
Accurately synchronizing the Schlieren movie to the turning on and off the magnetron is the big issue...
Maybe readers can point out what would be the most accurate synchronization between a movie and actual timing of the Magnetron turning ON and OFF...
It seems to me that the best way would be to have a signal showing the magnetron going ON and OFF in the movie itself (this would eliminate any errors due to the movie marching in time at a different, or non-monotonic rate than an external accurate clock). -
#279 by VAXHeadroom on 17 Dec, 2015 15:03
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Doc,
Yes, a video would both have a timer and contain audio to denote mag on (xformer hum).
Also, I could imbed a spectrum analyzer display in the corner to show freq locking, which would probably be a better indication of start.
Plume temp would be hard to measure with my IR thermometer...can get a case temp or sync a thermal vid.
Accurately synchronizing the Schlieren movie to the turning on and off the magnetron is the big issue...
Maybe readers can point out what would be the most accurate synchronization between a movie and actual timing of the Magnetron turning ON and OFF...
It seems to me that the best way would be to have a signal showing the magnetron going ON and OFF in the movie itself (this would eliminate any errors due to the movie marching in time at a different, or non-monotonic rate than an external accurate clock).
Tap a current sensor off the magnetron's electronic feed circuit and either turn a light on or just put an ammeter in the video. This would show when there's actually power going to the magnetron.