Do Dual Coils Affect TC Accuracy?

[Croak]

No, there's where you fail. If it's reading 1.5 ohms, it's 1.5 ohms. Period.

ONE

CIRCUIT

 

[Jalcide]

No, there's where you fail. If it's reading 1.5 ohms, it's 1.5 ohms. Period.

No, the two resistors inside this parallel circuit, what are they reading (when the combined circuit reads as 1.5 ohms)?

I need to hear a number, an actual value, of what you think the two resistors in this circuit are (each), in ohms, when the circuit reads 1.5.


(If you say "1.5" then I give up. Lol.)


One circuit, two resistors inside it.

 

[Croak]

For all intents and purposes, there is not two resistors inside a parallel circuit. There is (wait for it...) ONE. I don't know how to state this any more clearly.

 

[KenD]

I am absolutely acknowledging it's read as a single resistor.

Back to your example: It can't climb to 1.5 ohms unless each resistor inside it, climbs to 3 ohms.

Are we really not agreeing on this point?

By what sorcery are those two resistors exempt from following Ohm's Law? They don't even know about the "single" resistor they're a part of. Know what I'm sayin'.

No, we're not agreeing. It's not two separate resistors. When you combine the two resistors it becomes a single resistor. Sure, if you take one of the coils out of the picture it's no longer a single 0.5 resistor, it's a single 1 ohm resistor. It's about coil mass. Math is math, but it's an abstraction of a real world situation (plus I'm sure one who knows more about the math of these things will show that were actually dealing with a single resistor).

Sent from my M7_PLUS using Tapatalk

 

[Mactavish]

I'm calling the ASPCA.

 

[Croak]

No, the two resistors inside this parallel circuit, what are they reading (when the combined circuit reads as 1.5 ohms)?

I need to hear a number, an actual value, of what you think the two resistors in this circuit are (each), in ohms, when the circuit reads 1.5.

One circuit, two resistors inside it.

Let me spell it out

O
N
E

P
O
I
N
T

F
I
V
E

 

[Mactavish]

I'm calling the ASPCA.

Reason:

BEATING A DEAD HORSE!

 

[Jalcide]

For all intents and purposes, there is not two resistors inside a parallel circuit. There is (wait for it...) ONE. I don't know how to state this any more clearly.

Well, I just looked in my Vulcan dual fused clapton build and do, in fact, see two happy, healthy resistors inside it. Together, the mod sees them as one, but each coil isn't smart enough to know about that.

 

[Jalcide]

Reason:

BEATING A DEAD HORSE!

Agreed.

I really did want to have a fruitful, interesting discussion about a topic a lot of folks are talking about and having issues with now that TC has become so popular.

Edit: discussion continued... math continued... I was wrong about the temp difference due to the 2x ohm rise. See my later post where I run larger numbers based on Spirometry's work (to eliminate the chance that the temps were the same due to rounding of tiny miliohm changes).

As for answering this topic's question. Not entirely sure yet. Will let the discussion mature.

But I'm thinking it's mostly debunked.

 

[Croak]

 

[aldenf]

You're acknowledging there are two resistors and that it reads as one at "rest" (it's never really resting because of room temp fluctuations, but if that helps to visualize it). We agree. So take that a step further and agree that the physics of those laws don't mystically change as it heats and cools.

If you were to read the ohms on each resistor independently, while it was heating and cooling, It still has to follow the math of the resistors in parallel.

That means for every one ohm of resistance change the single circuit reports, two ohms of resistance must change in each separate coil of the circuit.

The math doesn't change just because interesting stuff is happening to the coils.

The point, Jalicide, is that the TC chipset has no clue there is one, two or ten coils in that circuit. It sees one resistor. As the TCR of a material doesn't change with mass, the only thing that can throw off the vaping experience is imbalance in the "sub-resistors". If we could read and control the coils independently, we could solve many of our issues. But that would require two discreet circuits in a dual-coil setup. If the two coils are not heating and cooling identically, that is an imbalance in the build. A multi-coil build for TC needs to be fairly precise, resulting in something that is far too involved and fiddly for me to bother with.

 

[KenD]

Agreed.

I really did want to have a fruitful, interesting discussion about a topic a lot of folks are talking about and having issues with now that TC has become so popular.

Sorry, all.

I'll close it.

Edit: Yikes, I can't seem to lock the thread.

All I can do is stop bumping the thread myself, which I will do.

As for answering the question this thread set out to answer: "Do Dual Coils Affect TC Accuracy?" I've personally arrived at the conclusion, and put forth my best reasoning as to why, that "Yes, they do."

Others appear to disagree.

The problem here is that you refuse to accept the facts.

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[Spirometry]

Do we at least agree that two 1-ohm resistors in parallel read as .5-ohms by an ohm meter (a mod)?

And that if the combined resistors heated up such that they read as 1.5 ohms, that each resistor would have to be 3 ohms (and therefore as hot as 3 ohms)?

And that the reverse of that, as it cools, is also true?

I'll agree to that.

And if the resistors were ni200 the dual coil(1.5Ω) it would be 353.33°C.

1.5Ω = 0.5Ω[1+(0.006(T-20°C))]
3 = 1+(0.006(T-20°C))
2 = (0.006(T-20°C))
333.33 = T-20°C
353.33°C = T
​

And if you did the calculations on each individual resistor(3Ω) it comes out to be 353.33°C.

3Ω = 1Ω[1+(0.006(T-20°C))]
3 = 1+(0.006(T-20°C))
2 = (0.006(T-20°C))
333.33 = T-20°C
353.33°C = T

​

Now we let the dual coil cool 1 milliohm as you said.

1.499Ω = 0.5Ω[1+(0.006(T-20°C))]
2.998Ω = 1+(0.006(T-20°C))
1.998 = (0.006(T-20°C))
333.00 = T-20°C
353.00°C = T
​

And here is the individual coil. And just like you said, because of ohm's law it will drop 2 milliohms.

2.998Ω = 1Ω[1+(0.006(T-20°C))]
2.998 = 1+(0.006(T-20°C))
1.998 = (0.006(T-20°C))
333.00 = T-20°C
353.00°C = T​

 

[drmarble]

Dual coils that are the same material/resistance will behave like a single coil and will not require any tcr adjustment.
The problem occurs when the coils aren't perfectly matched. The lower resistance coil will get the most current and get the hottest but the fractional resistance of both coils will not increase to match the temperature increase of that low ohm coil. The imbalance gets lower as the hotter (lower ohm) coil heats up more and its resistance rises. It will always be hotter than the other coil. This is a nasty, non-linear problem that I don't feel like solving. The differences would be even more extreme with a pair of clapton coils made with two different metals (Ti and Kanthal). Dual coils have to be very precisely matched to get good performance with TC.
(tldr I think that mismatched dual coils are the cause of the unexpected behavior. Matched dual coils behave like twisted pair coils which are like lower gauge coils (to a first approximation).

 

[Jalcide]

I'll agree to that.

And if the resistors were ni200 the dual coil(1.5Ω) it would be 353.33°C.

1.5Ω = 0.5Ω[1+(0.006(T-20°C))]
3 = 1+(0.006(T-20°C))
2 = (0.006(T-20°C))
333.33 = T-20°C
353.33°C = T
​

And if you did the calculations on each individual resistor(3Ω) it comes out to be 353.33°C.

3Ω = 1Ω[1+(0.006(T-20°C))]
3 = 1+(0.006(T-20°C))
2 = (0.006(T-20°C))
333.33 = T-20°C
353.33°C = T

​

Now we let the dual coil cool 1 milliohm as you said.

1.499Ω = 0.5Ω[1+(0.006(T-20°C))]
2.998Ω = 1+(0.006(T-20°C))
1.998 = (0.006(T-20°C))
333.00 = T-20°C
353.00°C = T
​

And here is the individual coil. And just like you said, because of ohm's law it will drop 2 milliohms.

2.998Ω = 1Ω[1+(0.006(T-20°C))]
2.998 = 1+(0.006(T-20°C))
1.998 = (0.006(T-20°C))
333.00 = T-20°C
353.00°C = T​

Woohoo!

Thanks for doing that.

Geez, I was about ready to take some night classes. I'll put the pin back in that idea... for now.

As for the rest of my wacky, controversial, lambasted hypothesis that something hot takes longer to cool to X, than something half as hot... I'll save that battle for another day when I have more fight in me.

Seeing as Croak bludgeoned me with some kind of Mad Max mace weapon back a couple posts, and left me for dead in a post-apocalyptic desert.

 

[Spirometry]

I was just trying to show, just because the atty dropped 1 milliohm and and the individual coil dropped 2 milliohms, nothing cooled faster than the other because they are the same temperature.

48 years old, can't believe I still remember algebra.

 

[Jalcide]

Dual coils that are the same material/resistance will behave like a single coil and will not require any tcr adjustment.
The problem occurs when the coils aren't perfectly matched. The lower resistance coil will get the most current and get the hottest but the fractional resistance of both coils will not increase to match the temperature increase of that low ohm coil. The imbalance gets lower as the hotter (lower ohm) coil heats up more and its resistance rises. It will always be hotter than the other coil. This is a nasty, non-linear problem that I don't feel like solving. The differences would be even more extreme with a pair of clapton coils made with two different metals (Ti and Kanthal). Dual coils have to be very precisely matched to get good performance with TC.
(tldr I think that mismatched dual coils are the cause of the unexpected behavior. Matched dual coils behave like twisted pair coils which are like lower gauge coils (to a first approximation).

Yes, lots of non-linear stuff there.

The hardcore "it's just one resistor, nothing else matters" camp, I think would say this shouldn't matter.

I of course disagree with this, and instead agree with your observation.

That said, I think the mismatched behavior gets averaged and smoothed out pretty nicely by the sample rate of the mod measuring, and probably ends up pretty close to half. Even if it's not half, it's close enough to point to the effect.

As for the non-linearity of the combined rises and falls of the two, I bet the sampling rate of the mod doesn't care too much. It's looking for threshold values at intervals that dwarf the effect of those non-linearities (I'm guessing).

 

[Jalcide]

I was just trying to show, just because the atty dropped 1 ohm and and the individual coil dropped 2 ohms, nothing cooled faster than the other because they are the same temperature.

48 years old, can't believe I still remember algebra.

Oh, sorry, I misread your post I think.

The 2 ohm coils must each cool an entire 1 ohm before the mod -- looking at the combined result -- thinks only a half ohm of cooling took place.

Do we agree that one?

I'm 47 and am right there with you, man.

I"m a programmer and still hate math. Lol. I avoid it all cost.

 

[Spirometry]

I meant to say milliohm. When back and edited it.

 

[BlueridgeDog]

In as much as the two coils are not identical, then there may be a balance issue that merits how they diverge from the "one circuit" philosophy. Yes, they are one, but will heat differently if there is even a slight difference in them. Is that averaged out as the over all resistance changes?