Flea Power Measurements

[ion]

So you want to measure the power output of your "Joule Thief" or other proposed OU device but lack a DSO or a true thermal RMS measurement device. Your waveform is rather crusty and you don't trust your metering or the level is too low to make meaningful calculations. You are tired of guessing at the power by the brightness of LED's

Not to fret. I have devised a simple method to determine the power output of your flea power device. This method, however can be scaled up for higher power measurement.

Items needed: A cheap indoor / outdoor thermometer such as a Radio Shack unit, or if you can get your hands on one, an expensive Fluke dual thermocouple thermometer, a 1/4 watt resistor, some styrofoam insulation and some tape. I found the Radio Shack unit to work well enough compared to my Fluke so I used it for the charts that follow.

Any 1/4 watt (250 milliwatt) resistor will develop a certain temperature versus power input when insulated from ambient, so you will need to tape your measuring probe to the resistor and surround it with some styrofoam insulation.

Now you need to subtract off ambient so a dual thermometer is handy. I have presented a chart of data painstakingly acquired over several days time. You can make your own chart or use this one.

You don't need to use 100 Ohms, any value resistor with a relatively small body such as a 1/4 watt unit  will develop the charted temperatures when the specified power levels for that resistor are present.

So you need only to hook the 1/4 Watt resistor of your choice (value hopefully impedance matched to your device) and measure it's insulated body temperature.

Then you can read the power developed in the resistor according to the temperature rise over ambient developed by the resistor.

Best to use a metal film precision resistor if you plan on making your own chart, as it makes calculations more precise (these types introduce less drift with temperature).

Any questions?

[BEP]

How do I account for all that free energy I'm pumping back into the battery powering the circuit?

(No, I'm not serious but your excellent and valiant effort will need an answer for this question.  )

[ion]

How do I account for all that free energy I'm pumping back into the battery powering the circuit?

(No, I'm not serious but your excellent and valiant effort will need an answer for this question.   )

Here's my answer to that:

The battery voltage should start to  overcharge and terminal voltage soar to well above nominal, in that case I would load the battery with the appropriate resistor value (and power rating) to get the voltage to level off to nominal float values. Now you can read the power returned by the temperature rise of that resistor or just measure the voltage across the resistor and use E^2 / R to see how much free power is generated.

In another method, I would replace the battery with a large capacitor, give it a kickstart and load the capacitor with the appropriate resistor to get the voltage to level off and stabilize. Then do the above.

I don't think we have to worry about that scenario yet !

[poynt99]

Excellent suggestion ION.

Your work is very much appreciated! I would encourage everyone to become familiar with this method. Me too.

[evolvingape]

Yes, excellent work ION.

When I read it earlier I just found myself nodding at the simplicity and the use of the scientific method. The line of best fit will identify replicable anomalies easily when compared to a control.

I am pretty sure that all of the current OU claimants in this area of science will not produce any results using this method, but for serious scientists it will be a big help!

RIM.

[Chet K]

ION
Geeze we owe you for this one big time !!
I can not imagine the countless hours this will save the community ...


And yes Measurements are fun,especially when you know how to do them  

Where do we sign up ?

Maybe we could learn on Larry's circuit??



Thx
Chet

[ion]

LT would be wise to at least check his DSO methods with an alternative. To make great claims and rely on only one test method can surely be a possible cause of error, especially if you are unskilled in DSO good practice,  skill in using the instrument and some of the fine methods POYNT has written about.

Thanks for all your support. I urge you to run a calibration test for yourself, and use this as a backup to other good instrumentation methods.

I have also run the resistor in free air, without insulation, but the temperature rise is not so high and flea power signals can get lost in the noise, so I prefer the insulated version with it's higher sensitivity.

This would not be necessary if we were talking real power such as watts or tens of watts. I started with this method to address the "Joule Thief" proponents with outputs in the milliwatt range, but the method is scalable to any power level.

In the future I'll be posting info on how to build a simple, direct readout power meter.......stay tuned.

[Itsu]

Works great ION, i used an insulated 1/2 Watt 330Kohm resistor (need it for the Tesla/Blocking replication from Steve which works up till 1000V i guess).

I made a calibration test from 25V till 396V (max. PS).
As my 330K Ohm resistor went from 333K till 323K when heated up i Incorporated this value in the calculations

(Be aware of the decimal point seperator which is a comma in Europe and i needed to use it in my excel spreatsheet)

Lets see what this Tesla/Blocking thingy can put out.

Regards Itsu

[PhysicsProf]

Good work, ION.

Any 1/4 watt (250 milliwatt) resistor will develop a certain temperature versus power input when insulated from ambient, so you will need to tape your measuring probe to the resistor and surround it with some styrofoam insulation.

From your plot, we see (for example) that 500mW results in a temperature-rise of approx 83F.  How much time does it take for your insulated resistor to reach this equilibrium temperature?

[Chet K]

Steve
I am so glad you asked the time question,I'm trying to get my head around the "Time" part
in this  well insulated protocol [as opposed to "fixed loss to ambient" Protocol ].

Thx
Chet

[ion]

Good work, ION.

From your plot, we see (for example) that 500mW results in a temperature-rise of approx 83F.  How much time does it take for your insulated resistor to reach this equilibrium temperature?

I let everything soak until there was no change in the fractional least significant digit, in this case 0.1F. This would take about 15 to 20 minutes per sample.

Of course, the insulation represents a thermal resistance to ambient, and the more heavily insulated, the higher the end equilibrium temperature. I used about one square inch of styrofoam wrapped with black electrical tape. More insulation will result in more sensitivity and higher temperature points along the curve of input power, so with the lack of a "standard"  insulation technique, each person should create a calibration curve for their unique insulation set.

The whole thing can be modeled as a resistor divider network with the thermal resistance to ambient being the lower part of the divider. We can refine this and get into more detail as there is more interest generated in this approach. There are refinements in lead dress, which will allow less leakage of our internal heat buildup to the ambient surroundings.

Itsu: Good work. You now have a calibrated curve for your load resistor. Next time perhaps use a precision resistor so you don't have so much delta R vs temp.

Bear in mind that once your curve is worked out for a particular value, any resistor value of similar body type will generate the equivalent temperature profile so you can use any preferred value that will impedance match to your device under test.

[ion]

Steve
I am so glad you asked the time question,I'm trying to get my head around the "Time" part
in this  well insulated protocol [as opposed to "fixed loss to ambient" Protocol ].

Thx
Chet

Chet: This is actually a fixed thermal resistance (loss) to ambient method, similar to the box or tent method, but with much better insulation. The tent or box method is for much higher output devices. We are talking flea power here.

This calibrated resistor method is for hooking up to small devices like Joule Thief circuits, where people are guessing at power out by eyeballing LED's. There are many ways to measure power, this is but one.

[TinMan]

Hi ION
I have an idea i would like to throw your way,in reguards to P/in and P/out measurements on a pulse motor.Could we use two incandescent bulb's insted of resistor's-as these are just resistor's that show the heat by way of light.If we have our supply battery hooked in parallel with a large value cap,and between the cap and battery we have a small incandescent bulb.The pulse motor would be drawing from the large cap(path of lowest resistance)and the current would then have to pass through the incandescent bulb to keep the cap charged to run the pulse motor.

On the output of the pulse motor,we would have a large cap with the same size incandescent bulb across that cap.We can then use a temp gun to measure the heat in both bulb's,and we would also have some sort of visual reference aswell.This way we would have a smooth DC input current flowing through the input bulb,and a smooth DC current flowing through the output bulb.We could also measure the voltages across both bulbs to use as another measurement of P/in and P/out.For this to work,the cap would have to be of a fairly big value-around 20,000uf,depending on the system ofcourse.

Your thought's?

[ion]

Hi ION
I have an idea i would like to throw your way,in reguards to P/in and P/out measurements on a pulse motor.Could we use two incandescent bulb's insted of resistor's-as these are just resistor's that show the heat by way of light.If we have our supply battery hooked in parallel with a large value cap,and between the cap and battery we have a small incandescent bulb.The pulse motor would be drawing from the large cap(path of lowest resistance)and the current would then have to pass through the incandescent bulb to keep the cap charged to run the pulse motor.

On the output of the pulse motor,we would have a large cap with the same size incandescent bulb across that cap.We can then use a temp gun to measure the heat in both bulb's,and we would also have some sort of visual reference aswell.This way we would have a smooth DC input current flowing through the input bulb,and a smooth DC current flowing through the output bulb.We could also measure the voltages across both bulbs to use as another measurement of P/in and P/out.For this to work,the cap would have to be of a fairly big value-around 20,000uf,depending on the system ofcourse.
Your thought's?

On the output side it would work, assuming you have a calibration curve of surface temp of the bulb versus power input for comparison.

On the input side, it is a bit trickier, since power on this side is a product of current through the bulb and source voltage. In other words to find input power, you need to multiply current times source voltage. Though we may know the current through the bulb, we cannot integrate into this the source voltage to obtain power product by a heat level alone.

So on the input side, you could use brightness of the bulb to obtain a value of current  passing through the bulb (assuming you had priorly created a curve of amps versus temperature). Once you get the relative amps from your curve, you can multiply by the source voltage to obtain power. We are also wasting a lot power to light the bulb, which is not delivered to our load, and must be accounted for.

A more exact way on the input side would be to use a one ohm precision shunt resistor in series with your voltage source. Now you can read voltage across the one ohm, which correlates directly to amps, and multiply this by the source voltage to obtain power.

I have covered the means to deal with the case of large pulses or spikes  on the shunt resistor by using a simple RC filter in front of your meter.

Checkout the posts on my bench under blocking oscillator efficiency tests.

[ion]

Because many folk may not want to get into a full computer controlled thermal bridge as outlined in my other thread, here is a simpler method that can determine the power output of your DUT.

I fabricated my build with very thin strands from type "J" ( Iron and Constantan ) thermocouple wire, wrapped and glued to 1/4 watt 100 Ohm resistors.

You could use very fine Copper and Iron, or Copper and Constantan for your thermo elements.

Each side was insulated with styrofoam to reduce the effects of air drafts, and raise the sensitivity.

The output from the self  powered unit is low but is easily read on my Fluke using the uA range setting.

The first method, (direct readout) requires a calibration curve to be generated.

With the null balance method, this is not necessary. You tune your power supply voltage for null and read power output on your power supply E X I. (I prefer this method).

You could use a dual thermometer. You could also use a powered bridge with thermistors, but I wanted to keep it simple and self powered. Also it is hard to sense the heat generated by those tiny resistors.

Although designed for power under a watt, it is easily scaleable to any power level with the appropriate sized resistors.

For greater output, additional thermocouples can be wired in series, but tips must be insulated electrically.

If you really want to build a quality thermal RMS power meter, see the attached datasheet. Linear Technology made a very nice chip to do the job, it is no longer available but you can use some of the ideas presented by the late master Jim Williams. See also app note 61 by Linear Tech.

[exnihiloest]

@Ion

Really interesting circuit! The LT1088 or equivalents is exactly what we need for power measurement of signals of any shape, I see no flaw. For big powers we can add external resistances, so there is no restriction. I was not aware of the existence of such circuits. They drastically simplify the RMS measurements. Thanks  

[Chet K]

exnihiloest


I hope this makes it through the language barrier
Some things by there very nature are self evident ,......I hit my thumb with a hammer it will hurt.

It has been my life experience that this Model works in other areas ....certain observations become "profound"!!

When I man with Skills and experience Like ION is interested in something such as the SM device ,To me it becomes "Profoundly obvious"there is much more than "faith" at work..............

A casual dismissal is inappropriate !
thx
Chet  
PS
Sorry for the off topic ,I will remove this post by tomorrow.....

[BEP]

ION,

Your willingness to share such simple but excellent solutions is inspiring 

I think folks should use the comparative method with the DC circuit & power supply. That should convince anyone.

To think I bought a Bird 4421 for performing such measurements. Of course, at the time the customer wouldn't have accepted such a simple arrangement even though the accuracy of your method can be just as accurate as the Bird with proper application and use.

I have a couple of full reels of LM50C's I'm willing to share with fellow forum members for the price of return postage if anyone develops a method to use them accurately. I can build a POC before anyone commits to the cost of postage 

[ion]

Thermocouple wires, when cut from the same spool, can be very well matched , far better than any other temperature sensor except perhaps a quality platinum RTD, These other sensors are fine but must be hand selected for match.

In the self powered balance bridge method, matching is the important issue, not absolute accuracy. I have some AD590's, thermistors and some lower quality platinum RTD's on hand. For ultimate simplicity I chose the thermocouples.

I chose a self powered regime using the inherent matching that comes from thermocouples cut from the same length of wire.

Granted the temperature IC sensors and other types have higher gain, but the need for a power supply and hand matching ruled those out.

+/- 3 C initial accuracy of the LM50C would mean matching is necessary if you want accuracy in your bridge. The resistors should also be matched and capable of the expected temperatures without excessive drift.

Of course the LM50C's (or any IC sensor or thermistor) will work just fine without matching if a zero adjustment is inserted in the bridge. You could also use the neg tempco of diodes or transistor junctions in a bridge with zero adj.

Thanks for the offer on the LM50C's they are handy little devices, I might take you up on a few.

[BEP]

I have a reel of LMC6482's which were used in the same bridged LM50C design. I'm sure I have the calibrated voltage sources, as well. I just need to find them.

Matching shouldn't be off by much they were ordered as matched but I don't remember the specs.

These were used in a MV motor starter pole sensing circuit design I did about 15 years ago which included MLX series Hall-effects. I have a ton of those but they are useless unless programmed.

When finished, that circuit had a very long life of reliability and repeatability with an accuracy of better than 1%. At least UL & CE liked it 

The voltage references were key. I'll continue to look for them after all of the eggs are found and the grandkids have passed out 

[exnihiloest]

..
I hope this makes it through the language barrier
...

I'm afraid that this didn't. I just thanked Ion for his proposition of using the LT1088 which is a bright solution. No irony from me, the matter that I regularly see from Ion is always relevant. So I'm surprised that there is a comment about my reply and I don't understand what you mean with "dismissal"  .

[TinMan]

exnihiloest


I hope this makes it through the language barrier
Some things by there very nature are self evident ,......I hit my thumb with a hammer it will hurt.

It has been my life experience that this Model works in other areas ....certain observations become "profound"!!

When I man with Skills and experience Like ION is interested in something such as the SM device ,To me it becomes "Profoundly obvious"there is much more than "faith" at work..............

A casual dismissal is inappropriate !
thx
Chet  
PS
Sorry for the off topic ,I will remove this post by tomorrow.....

[Chet K]

HHMMMm
Since you copied the post I'll respond where this particular topic is more relevant
the TPU thread

thx
Chet

[gyula]

Hi Folks,

I would like to show two circuits for measuring low power (uW-mW) waveforms in a wide frequency range, besides ION's contributions. I dig the circuits from old Ham Radio Magazin articles.  This magazin was finished existing in 1990, first issued in 1968, so I hope no copyright issues involved to show some pages from it.
From the first article I show first the schematic and if there is interest to build it I have the full article to upload, alltogether 6 pages. The second article is a one page long only.
I did not build the first circuit, and I tested the second circuit many years ago with an old Selenium photo cell , wrapped it up with a grain of wheat lamp into an Alu pipe and it worked nicely. I improved it a little by including the tiny lamp in a resiistor network to make it even less frequency dependent and to have a quasi brightness independent input impedance, this way the rf current indicator role turned into approximately a 5-10% accurate rf power measuring device with reasonable bandwidth but with some ten mW and higher sensitivity.

Gyula

[ion]

gyula:

Thanks for the circuit upload, and your interest in low power measurements.

Regarding the first circuit, notice that the input is  AC coupled with a 0.01 uF capacitor. This limits the low frequency passband, so the circuit as drawn is rated from 1 MHz to 500 MHz. In other words, it will quickly roll off sensitivity below 1 MHz and not work well with very low frequency signals.

It can be modified to work down to DC. The use of light bulb filaments will work, but provide an extremely non-linear input impedance and transfer function.

If you can, upload the rest of the article as I enjoy understanding the designers intent.

Thanks again.