You absolutely must use Titanium 1 - Titanium 2 is not considered safe to vape. Check out this thread for lots more info:
Titanium wire, vaping and safety
And it is Titanium 1 that I have measured at 0.0035 - despite what those figures might indicate. The figures in literature do vary - I have found figures as high as 0.0042 for Titanium.
But there's one very important thing to note: TCRs are not necessarily flat across the entire temperature range. When a single TCR figure is given, it is usually an average over a large temperature range. It is therefore not guaranteed that the TCR will be that same figure within any given part of the range.
In the case of Titanium this temperature range may be up to 600 or more degrees C - so that figure of 0.0037 is from 20 - 600°C (or similar high number.) But for vaping, we only care about the range 20-250°C, or 300°C max.
Titanium's TCR graph is fairly flat up to a point, and then suddenly changes tangent. I believe that point is around the curie point, which I seem to remember is around 350°C-400°C.
There's more info and discussion on this in this thread:
TC beyond Ni200: Nickel Purity, Dicodes; Ti, SS, Resistherm NiFe30; Coefficient of Resistance
in particular looking through the last 15 pages or so for posts by
@vapealone . He has put together a Google Spreadsheet with TCR data gathered from the web, for various wires. On this he has plotted graphs, which can be used to see the TCR at different points in the range. Using that data, we might find that the TCR for the whole Titanium temp range is 0.0037 or similar. But we only care about 20-300°C.
His data comes from published data sheets on Titanium Grade 1. He doesn't use a single TCR figure, but rather he uses the recorded resistance offsets at given temperature. You will see these charts on many metal/wire datasheets. It will usually show a horizontal, two-row table, showing the resistance factor at 20°C, 200°C, 400°C, 500°C, etc (the increments vary in different data sheets.)
So it will indicate that if the resistance is 1.0Ω at 20°C, it will be 1.XXΩ at 200°C, 1.YY at 400°C, etc. It's that data that vapealone has recorded and then graphed to work out the TCR.
In any case, I am satisfied that the Titanium Grade 1 I am vaping on
* has a TCR of 0.0035 for target temperatures of 200°C - 250°C. Or at least, the setting on the Dicodes mod should be 0.0035 - which I am currently assuming to be the same thing! When I next do this testing, I will also be testing using the DNA 200. I hope to find matching figures across both, allowing me to be sure of that result; I can then use that to verify the accuracy of other mods, using the Dicodes+DNA 200 result as my benchmark.
* Or to be precise, one brand of the Titanium Grade I have tested. I have not yet temp tested the other brands, only confirmed - subjectively - that the same temp setting + TCR setting gives a comparable vape. I plan to test more brands soon.
However, unlike Ni200, we can be fairly confident that if one Titanium Grade 1 tests at a certain TCR, so will the others. Titanium Grade 1 appears to have a much narrower specification. Ni200's spec is that it is 99.0 - 99.6% Nickel. 0.6% may seem like a small amount, but I already know from testing that the TCR can vary hugely. The expected single TCR figure for Ni200, in our vaping range, is 0.006. I have Ni200 that matches that, and I also have Ni200 which needs a TCR around 0.0045 - and which therefore needs temperature offsets on any Ni200 mod that doesn't allow modifying the TCR! Such as the DNA 40. It's good quality wire, within specification, it's just the spec is wide enough to vary the TCR quite significantly.
My point being that this appears not to be the case with Titanum. The spec is, I believe, narrow enough that if one brand of Titanium Grade 1 measures TCR 0.0035 so will all the other Titanium Grade 1s - or certainly very near.
But I have confidence this time.
