strange coil ohm problem

[rastapete69]

I am fairly new to wrapping coils but feel like I am getting better.

Today, My Igo W arrived and I built a similar 10 wrap coil on Kanthal 28 that I have been having similar problems with.

I take it off the drill bit, pinch it with tweezers, install it and check the ohms, which typically read around 1.6.

Once I get it fastened it I am finding the ohms jump to 2.4.

 

[AttyPops]

What did you use to check the ohms? What was the process?

 

[rastapete69]

Pushing the vv and vw button at the same time on my MVP which measures ohms.
How accurately I don't know.

I'm still learning, but this mostly happens on my RDAs as I seem to have a tough time lining up the coils and getting the ends screwed down, which was one of the reasons I went with the Igo W and the post holes.

 

[AttyPops]

...snip...I take it off the drill bit, pinch it with tweezers, install it and check the ohms, which typically read around 1.6.

Once I get it fastened it I am finding the ohms jump to 2.4.

OK, I don't understand. Help me understand. How do you attach it and check the ohms, and then fasten it later?

 

[DaveP]

I would have thought that the resistance would drop on the mod versus the ohm meter. Unless you have an auto zero meter the lead resistance will kick up the reading by the resistance of the lead connections.

Measure the coil using your voltmeter on the ohms setting. Stabilize the lead resistance and clean the plug in connections on the meter and subtract that from the actual reading of the coil, then compare it to the MVP internal reading. Something is out of calibration somewhere.

I wound a coil last night and checked it with the meter after installing it on my Protank head (before I put it in the Protank). When I vaped it and then checked it using the Provari internal resistance check I was within .2 ohms of the voltmeter reading before it was heated and then checked on the mod.

 

[AttyPops]

I would have thought that the resistance would drop on the mod versus the ohm meter. Unless you have an auto zero meter the lead resistance will kick up the reading by the resistance of the lead connections.

What ohm meter?

 

[DaveP]

What ohm meter?

He didn't mention one. I'm assuming he did. Either that or his IGO features multiple value readings. We do know that he didn't compress a coil and lower the resistance. I'm wondering what the difference is between installing and fastening. More information is needed.

I like to check them cold on the meter before I install and hit the fire button. It should be the first check for mech users. He's using an IGO with variable wattage. Doesn't it have short protection?

 

[AttyPops]

Well, his problem is on one side or the other (assuming the coil ohms don't change because it hasn't "fired" yet).

So, either the ohm check he's doing before he puts it on the MVP is wrong, or the MVP side is wrong. But I can't tell what he's doing...

OP: Clean the threads on the MVP including the center post. That's the higher of the two, so most suspect. Also, if using an inexpensive Digital Multi Meter (DMM) sometimes they don't read low resistances very well. So IDK.

 

[Btsmokincat]

The first time I made a microcoil I got crazy ohm readings on my MVP2. Turns out I didn't have the screws holding the wire tight enough. Double check that the screws are tight and that the coil isn't touching the deck or a post.

 

[DaveP]

The first time I made a microcoil I got crazy ohm readings on my MVP2. Turns out I didn't have the screws holding the wire tight enough. Double check that the screws are tight and that the coil isn't touching the deck or a post.

Loose screws would do it.

 

[VaPreis]

I am fairly new to wrapping coils but feel like I am getting better.

Today, My Igo W arrived and I built a similar 10 wrap coil on Kanthal 28 that I have been having similar problems with.

I take it off the drill bit, pinch it with tweezers, install it and check the ohms, which typically read around 1.6.

Once I get it fastened it I am finding the ohms jump to 2.4.

My experience with the Igo-W is that the screws like to come loose. Particularly when fitting it with dual coils.

 

[rastapete69]

OK, I don't understand. Help me understand. How do you attach it and check the ohms, and then fasten it later?

Sorry to if I'm being vague.
I wrap the coil, install it in the atty, then check the ohms.
At that point, I wick with cotton and find the coil normally needs minor adjusting at which point the ohm reading jumps up.

 

[rastapete69]

I'm thinking an ohm reader might be necessary as I am not fully trusting the reading directly from the MVP.

 

[AttyPops]

No problem.

Let's assume for a second that the screws where OK/tight. (Because that's easy to check and fix if that was it...you've already been given that good advice).

The only thing I can think of is that oxidizing the coil and settling it in (particularly if you fire it) will change the ohms. Do they stay consistently at 2.4 after it settles down? If so, that's the result. And the 1.6 was due to micro-shorts in the coil before it got broken in.

Guessing here.

 

[rastapete69]

That actually sounds very logical AttyPops, thank you.
I've been kind of obsessing over this and ripping out the coils and starting again, but can't say the 2.4 ohms were vaping bad.
What confused me a little was the fact that I have been having success with microcoils and cotton wick in my protank heads and figured the RDA's would be a breeze considering all the extra space to work with.

 

[AttyPops]

Yeah. When people do microcoils, they often "fire them" until they "glow evenly". Glow evenly is a code phrase for getting the current to flow properly in the wire...AKA no shorts. Squishing the (new) wires together can create shorts. And the firing makes the coil wire expand, cool down and shrink, and oxidize too...eliminating shorts and increasing ohms to where they should be.

IDK if you'd have different results if you oxidized/annealed the wire first...like over a flame. Would be an interesting experiment.

I don't usually do micocoils...the center gets too hot for me, IMO. I just wrap with space between the loops. But to each their own...not dissing microcoils at all. Just stating that I'm not an MC expert.

 

[rastapete69]

Funny thing happened when I got home.
I tried a coil again and put less pressure on it and it read 1.5 ohm
After carefully attaching it to the posts and tightening, the wick went in and it stayed at 1.5 and has stayed there for some vaping

I believe you may be right about the short from squishing Attypops.

My method had always been to torch the kanthal before wrapping, wrapping on 5/16 drill bit, pulling off drill bit, pinching with tweezers and torching again, then installing.

I believe I got this method from a Rip Tripper video, but probably overdid it like everything else I like!

I'm now under the impression I might be too rough on the coils.

Thanks for all the insight and sharing your experience

 

[dedi]

Yeah. When people do microcoils, they often "fire them" until they "glow evenly". Glow evenly is a code phrase for getting the current to flow properly in the wire...AKA no shorts. Squishing the (new) wires together can create shorts. And the firing makes the coil wire expand, cool down and shrink, and oxidize too...eliminating shorts and increasing ohms to where they should be.

IDK if you'd have different results if you oxidized/annealed the wire first...like over a flame. Would be an interesting experiment.

I don't usually do micocoils...the center gets too hot for me, IMO. I just wrap with space between the loops. But to each their own...not dissing microcoils at all. Just stating that I'm not an MC expert.

Don't mean to be butting in here but just want to clarify with you AttyPops...........I have never done a micro (planning to for comparison though) Are you saying that with regular coils they need to "settle in" or whatever term you used? I had the same happen with my last regular coil. Tested on multimeter, MVP and Provari, it jumped around a bit. It glowed from center outward and no hotlegs, but still bounced a bit. I was aiming for 1.7 to 1.9. It bounced 1.5 to 2.0 and settled at 1.7 on everything. So I figure good to go I didn't know about the "settling thing". This is on a mini octopus.

 

[crxess]

Settling in includes getting the coil legs to channel current smoothly through the post. This does not happen simply by securing the screws. As current is passed through a few times a path is firmly established and things settle down. Any fiddling. adjustment, screw movement and the process may start all over.
People always talk about BBC coil head readings changing. It is the same thing only exaggerated due to the Legs being held in place by a rubber grommet and pressure rather than a secure attachment. Any flexing movement, pin pulling can change the contact points and readings will usually jump up.

 

[Don Robertson]

IDK if you'd have different results if you oxidized/annealed the wire first...like over a flame. Would be an interesting experiment.

I did just four coils today; my first for T3s. I annealed the wire for two and on the other two I did a 'burn' of only the coils.

ANNEALED COILS = 2.0 ohms

NOT ANNEALED COILS = 2.4 ohms

BURNED COILS - NO WICK = 2.1 ohms.

Sort of contrary of what I expected.

Senile Old Man Don ..... Will probably forego building my own a BUY pre-wrapped coils with wick from FastTech. Less labor - cost effective and a heck of a time saver IF they work well.