Coils and What They're Made Of
To understand '' Why Does My Coil Resistance Keep Changing '' , you need to understand a bit about what coils are made of :
Coils are made up of strands of resistance wire made of metal alloy. Metal wire heats up when you vape on it which in turn evaporates your E Liquid to produce vapour. The makeup of the resistance wire is important as it determines how the coils will behave when you heat them up. Typically you will find most coils whether bought over the counter premade or in spools of wire for custom builds are composed of one or more of the following :
.Nickel Chromium otherwise known as A1 Kanthal - For use with standard variable wattage mode
.Nickel Ni200 - For use with temperature Control
.Nichrome (Nickel Chromium but heavier on the Nickel ) Ni80 - For use with standard variable wattage mode to decrease ramp up time
.Titanium TI -For use with temperature Control
.ss314 Stainless Steel - For use with temperature Control or Standard Variable Wattage applications
To see which one you are using, simply check your coil's packaging for any of the above classifications. Then look at how you are trying to run your mod with them. Are you using the correct mode for the type of coil ? If your problem has just been resolved , then that's great ! If not , we'll have to just keep going...
Temperature and What it does to Metals
So Let's go back to basic physics here. Metal expands when it heats up and contracts when it cools down. So what does that actually mean for Vapers ? Well , resistance is determined by how wide your conduit or 'pipe' is. So when you have a wider pipe, more water can flow through it. Coil wire is the same. Heat it up and the molecules have more electrons between them causing the conduit to widen and the resistance to drop. When they cool, the electrons have left via your vapour and the conduit shrinks again causing an increase in resistance. This generally accounts for small variances of between 0.1 ohm and 0.2 ohm in A1 Kanthal and in Nichrome 80 as well as SS314. Larger variances usually mean you're either dealing with Ni200 or TI coils or you have a problem with your coil or build.
Troubleshooting Major Coil Readout Issues
Standard Variable Wattage:
First thing's first. Know your device. What coils can it fire, what the minimum resistance load is, what modes does it support. Are you using the correct coil type for the mode you're in ? Have you read the manual ? It really pays to check this stuff out before you panic and think you have a fault or broken device. Check your coil is fitted into your tank or dripper nice and tight. Most issues are related to poor connection. Check it several times.
This is because it may have appeared to be working great before a couple of puffs but since then, you've put it through a heat cycle. It may need an adjustment after that. This is especially true with thicker , complex wire builds like Fused Claptons, Alien wire , Stapled wire or any combination of that sort. As your wire becomes malleable after heating, the post screws often need a little tighten up to take up the slack as the wire flattens inside the posts. If you have a spare coil,(when using factory coils) try it, to see if you simply have a faulty coil.
Try your tank or dripper on another device and see what happens there. Basically you need to cross reference for connection errors by process of elimination. If that still doesn't resolve it, then finally check your rubber O rings and isolators. Not so much the ones sealing your tank. More so the ones isolating your positive and negative/ ground terminals of your coil or atty. The 510 connector is a good one to check as these can be overlooked by manufacturers for heat tolerance. Finally take time when shaping your coils , if you're building them yourself. The deck may feature PEEK insulators which are heat resistant up to amazingly high temperatures but not all decks have PEEK and the 510 connector is almost guaranteed not to on many RBA's etc. If you dry burn the coils for too long the deck and base of the tank or dripper will get so hot that your could be melting your 510 isolator.
Problems Unique To Temperature Control Modes :
Most temperature control issues come down to calibration. Its actually rather simple. The chip is expecting you to fit a coil at room temperature. So when you screw the tank or dripper on, the chip will ask if you have fitted a new coil. At this point it'll also be asking you what type. Make sure you are fitting your coil at room temperature. Select the correct designation of coil type and BAM, your coil is now correctly installed. Don't go firing it and then re-installing it to your mod at 400 degrees. Your Mod won't understand what's going on and it'll work badly. Likewise if your coil has been in a box in your car in the dead of winter all day, Don't install it like that. Wait until you get to a room with normal temperatures and wait 10 or 15 minutes before you install it.
If you've gone through all the steps and advice above and you're still suffering with issues then you may in fact have a manufacturing flaw in your tank or dripper. Maybe it's a rebuildable atty ,then I presume you know the coils should not be touching the deck or outer wall of the chimney section. If they are then get a mate to slap you 'round the face as that's a rookie error. Seriously though if this guide hasn't resolved your issues and you're getting dramatic changes in your resistance readout then take your gear back to the store you purchased from. They will check it over and if they can't resolve it maybe they can swap it out or help you find something better.
Hopefully that has now got you sorted for the '' Why Does My Coil Resistance Keep Changing '' problem.