Does saline solution change the resistance?

[Giraut]

I have this weird problem that might be related to the saline solution I use in my juices. Whenever I squonk too hard and flood my atty, my mod quits working and reports "low load". When that happens, the built-in ohmmeter reports 1.2Ω - and my mod is designed to refuse to work at 1.2Ω or under.

Normally, the coil reads at 1.4Ω. If I open the atty and dry up the coil with a paper towel, it goes back up to 1.4Ω and the mod starts working again.

I wonder if this is due to the added salt in the juice. I don't use very much - one drop of 0.9% saline solution per millliliter of juice - but maybe that's enough to cause the 0.2Ω resistance drop I'm seeing.

Has anybody noticed that?

 

[dannyv45]

I noticed it on my vamo with a kayfun. The resistance does change sometimes and I don't think it's related to salt. I see it in my saline and non saline mixes. If I'm to close to that 1.1ohm cut off with my coil it will happen. That's why I wind to 1.3 or 1.4. So if you wind you coils I would do 1.5 or higher.

 

[Giraut]

Yeah I'll make it higher. Usually I'm closer to 1.8, but I messed this one up. I was just curious.

 

[Crunktanium]

Depending how hard you crank down your tank, the type of metals used in the construction of your mod/tank. Plus a whole lot of other variables can impact your coil reading. The salt itself can allow a greater flow of current which can have an effect similar to a drop in resistance. Basically the saline may be providing a better contact (similar to using dielectric grease) between the metals within your tank and the battery. So yes salt can in fact cause the resistance to drop by a small amount. But also depending on how well/tight your coil was wrapped/secured just knocking it about from normal use can also change the resistance slightly.

 

[JohnnyDill]

Seems that the electrolyte from the dissolved salt is improving current flow. Interesting chemistry going on there.

 

[Cloudcomm]

I like the theory JohnnyD but the resistance of the resistance wire shouldn't change unless it is damaged or overly heated. I would offer another theory of, the salinity may be causing shorting or current to jump coils. His Atty doesn't like this and goes into overload protection. I will test this with a micro coil, given the most chance of shorting. One with .9 sterile saline and VG, one with strait PG. I will use new micros built with 30ga giving a resistance of about 1.5ohms. Give me a couple hours, gotta watch Deadliest Catch.

 

[MorpheusPA]

Saline is electrically conductive, although you don't seem to be using terribly much. I'd think the impact would be minimal, but in your case, minimal is enough to throw you under the lowest resistance you can use.

Salt bridges are fairly common, and used in things like batteries. In those cases, though, they're pretty concentrated to carry a lot of power at low resistance.

 

[Cloudcomm]

Tested both at 8watts, 1.5ohms to start on both coils, no change to either coil after firing several times. Even noticeable warmth to the touch still 1.5ohms.
Conclusion =.9% Saline blended with VG at 15% does not alter the resistance of micro coils of 1.5ohms fired at 4-6sec at 8watts.
I do concede as stated by Morph the possibility of salt bridges causing an anomaly either shorting or jumping voltage around/along ie"skin effect" the resistance wire. Faulty wire, cracked wire, kinked wire and of course sloppy connectivity could all cause fluctuations in current carrying capability of the coils/atty setup.
It was a fun project. Now I know what unflavored juices taste like

 

[Giraut]

Thanks Cloudcomm - very interesting!

 

[MorpheusPA]

Tested both at 8watts, 1.5ohms to start on both coils, no change to either coil after firing several times. Even noticeable warmth to the touch still 1.5ohms.
Conclusion =.9% Saline blended with VG at 15% does not alter the resistance of micro coils of 1.5ohms fired at 4-6sec at 8watts.
I do concede as stated by Morph the possibility of salt bridges causing an anomaly either shorting or jumping voltage around/along ie"skin effect" the resistance wire. Faulty wire, cracked wire, kinked wire and of course sloppy connectivity could all cause fluctuations in current carrying capability of the coils/atty setup.
It was a fun project. Now I know what unflavored juices taste like

From your test, it doesn't seem likely to be having an appreciable impact. 0.9% saline...I wouldn't expect it to. That's what blood is, and it's not much of an electrical conductor at about 150 ohm-cm.

Don't ask how I know that. Let's just accept that I do and move on without questions, OK?

 

[Giraut]

From your test, it doesn't seem likely to be having an appreciable impact. 0.9% saline...I wouldn't expect it to. That's what blood is, and it's not much of an electrical conductor at about 150 ohm-cm^

I'm not sure a bulk resistivity value applies to a thin film of solution on the surface of a coiled wire strung between the two posts of an atty.

Still, I believe you're right: for the sake of reasoning, assuming there's a 5 mm gap between the posts, assuming your value is correct, and assuming there's a solid bridge of blood-equivalent juice between the posts, that works out at 75Ω for that bridge of juice.

With the 1.5Ω coil - that's essentially a resistor in parallel with the "juice resistor" - that makes an equivalent resistor R=1 / (1/Rcoil + 1/Rjuice) = 1.47Ω. So, essentially, it's negligible.

Don't ask how I know that. Let's just accept that I do and move on without questions, OK?

The only person I can think of who would know the electrical resistance of blood is Dr. Frankenstein

 

[Bryong70]

My rebuildable reads wrong ohms on occasion, only cause I didn't tighten down the posts for the coil legs, or they get loose.