Do Dual Coils Affect TC Accuracy?

[stylemessiah]

This beats Santa

 

[Jalcide]

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

Gottcha. I'd be interested to see it with larger values so that we can point to a net effect.

A milliohm is so tiny, used like this.

Will do the calculations later (not asking you to)

Based on the notion that two, 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.

 

[Jalcide]

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?

I think the slightly mismatched coils would heat pretty consistently from time to time, but with non-linearities over the duration of the rises and falls that translate into small peaks and valleys of TCR inaccuracy, from how the mod sees it.

I'm not sure, I'd need to test. I think some of this is smoothed out because of how fast the mod reacts.

 

[Croak]

Gottcha. I'd be interested to see it with larger values so that we can point to a net effect.

A milliohm is so tiny, used like this.

Will do the calculations later (not asking you to)

Based on the notion that two, 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.

Your assumption is that each coil is heating up twice as much as a single coil would. That is not the case, and why I keep hammering the single circuit point. Single circuit. Resistance divided. Current divided. Heat divided.

Divided exactly equally in real world, hand wrapped, eyeball measured coils? Probably not, but you can still get "horseshoes and hand grenades" close, well within the margin of error for the level of measurement accuracy current TC mods possess.

Your other assumption seems to be that the resistance reading is merely a construct, based on your "how the mod sees it" statement. The mod sees it how it is. It's called Ohm's Law for a reason. Not Ohm's Strongly Worded Suggestion.

But why don't we change tracks a wee bit. We'll stick with a single coil. But let's compare two different single coils, one with a higher mass and lower resistance, and one with a lower mass and higher resistance. Say a 24ga 10 wrap vs a 30ga 5 wrap, both in the same material of your choice. Apply your theory to that. Then make two more coils, this time both using identical gauge wire, with one coil having twice the wraps, compare again.

Why doesn't your theory hold up in either case? See where I'm going with this?

 

[KenD]

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).

No, would not disagree with that. It's still one resistor, but the two parts of it are uneven. The unevenness is a major problem. Yes, the tc will even out the temperature, but that will lead one of the coils heating up more, possibly much more, which can lead to either dry burns or anemic vape.

Sent from my M7_PLUS using Tapatalk

 

[Jalcide]

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.
.

I ran the TCR math on some more real world values...

You are right, Spirometry.

I was wrong.

The rise and fall of twice the ohms in the parallel circuit does happen, like I suspected, but like you said, the math of the TCR formula, when paired with parallel resistor math, works out to keep the temperature the same in each coil, between dual and single.

Here's the math for a .15-ohm Ni200 build, with a .1 ohm rise and drop in resistance:

TCR formula:
(Rref + rD) = Rref [1 + a(T - Tref)]

R = resistance at temp T
Rref = resistance at temp Tref
a = TCR
T = temp
Tref = ref temp for the TCR
rD = resistance delta (rise)

Single coil build TCR formula:
(.15 + .1) = .15[1 + .006(T - 20)]
A .1-ohm rise and fall equates to 131.1C, or 267.9F.

For the dual build to read at .15-ohm, each coil needs to be .3-ohm.
So the same .1-ohm rise of the circuit, means each resistor inside it must rise .2 ohm.
Dual coil build TCR formula:
(.3 + .2) = .3[1 + .006(T - 20)]
A .2-ohm rise and fall required for each coil equates to 131.1C, or 267.9F

Well, F. me. I need a vape and some scotch.

 

[stylemessiah]

I have to unsub this thread

Theres maths here

Once it gets beyond counting fingers and toes level i feel completely adrift

I need an anchor

Hint: it will include an inordinate amount of sugar

Please, in future, limit your replies and theories to indicate the feasability of a concept using either one of the following terms

Workies

No workies

 

[cheech226]

imo if your tc dual coil vape is anemic there is a problem with the build/hardware. i'd use a word like "stunning" to describe the vape from my goblin mini as compared to my stm.