In all honesty, it should not matter where the standard comes from (assuming you want to spend the cost of a full test kit on just one standard). If the standard is offered as a "NIST Traceable" standard, then it's manufacturing has to conform to a precise set of conditions and practices in order to obtain a NIST Certificate (and NIST will have confirmed it's exact value as an independent source). It's similar to how a manufacturing facility can only obtain an ISO certification if it conforms to set of perquisite conditions as well as on-going monitoring.
I would caution against getting too caught up in all of this. NIST-traceable standards are often very expensive and you could easily spend the cost of several test kits worth of money on these standards only to gain very minimal and statistically meaningless information...but have at it if you wish....
I understand that after all of this that I may simply prove that my system is sufficiently accurate for my purposes, which is really what I want. I would like to understand if the NIST sample for example for cyn is 50, that if my readings are 53-47, then good. I also understand the costs can be a bit, but that can be countered over time by not over/under chemical feeding of pool.
I read/seen a wide variance of opinions on various testers from users claiming one better than the other. Ideally I would love to see a independent review of the various kits from an impartial reviewer (yes redundant)
using NIST standards.
When I look at a piece or audio, or video, or test gear, I can find reviews that measure performance with real test gear with well defined methods, which are repeatable. So I was hoping to find the same for these tests.
So, yes maybe I am being too picky and should just accept that its working, but from my background it hard.
Thanks
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Why not just perform an MSA on the ColorQ and on a Taylor k2006 and on the TF 100? The results of an MSA don't really care about the "exactness" of the tests, but more on techniques and repeatability and consistency.
If your sigma values are very different, you will have your answer.
Sorry, not familiar with the term MSA.
Without knowing the actual value, the range alone is not enough. For example, if test A shows ph as 7.55 - 7.45 and test B show PH as 7.71-7.69, which is better? If I know the real PH is 7.5, then I could live with either if I know they are consistent, but would probably prefer test A since if is closer to real value, even though the range is wider.