Would it be practical to prepare CYA reference solutions to aid in testing?

[Orion7319]

Differences in perception to try to make a standardized test is a problem but I only need to calibrate my own eyes lol.

Exactly! I don’t think your going to need a 225nm UV led and a photometer though to tell the difference between 40 and 50 or 50 and 60 and so on… unless you absolutely have a passion for calibrating photometers and playing with UV lights. I would love to see the write up on that one though! Lol!
Bonus points if you can somehow incorporate an arduino board in that project..

 

[SoDel]

Exactly! I don’t think your going to need a 225nm UV led and a photometer though to tell the difference between 40 and 50 or 50 and 60 and so on… unless you absolutely have a passion for calibrating photometers and playing with UV lights. I would love to see the write up on that one though! Lol!
Bonus points if you can somehow incorporate an arduino board in that project..

Probably use ESP32 for the SOC part of it — just more familiar with that lol.

 

[DrewLG]

The melamine cyanurate scatters the light (I assume entering the tube from the sides) to make the dot disappear, but the lighting has to be “just right” for that to happen accurately and repeatably. When the 50 ppm standard comes in, I’ll try some experiments with some sort of adjustable lighting setup.

You may be overthinking this.

Repeatability is the main thing, so you can see long-term trends in CYA over a month or two. You don't really need absolute accuracy, and unless you're regularly draining/replacing a lot of water for some reason, you REALLY don't need to chase CYA week-to-week. Look again at the FC/CYA chart -- there's very little difference between what you'd do to maintain your pool at 50ppm and what you'd do at 40 or 60. That's why the test rounds up: If there's an error, the rounding pushes it in the direction of more FC for safety. And that's ok because it's only barely more FC.

 

[SoDel]

You may be overthinking this.

Repeatability is the main thing, so you can see long-term trends in CYA over a month or two. You don't really need absolute accuracy, and unless you're regularly draining/replacing a lot of water for some reason, you REALLY don't need to chase CYA week-to-week. Look again at the FC/CYA chart -- there's very little difference between what you'd do to maintain your pool at 50ppm and what you'd do at 40 or 60. That's why the test rounds up: If there's an error, the rounding pushes it in the direction of more FC for safety. And that's ok because it's only barely more FC.

Of course I’m overthinking it; that’s my job lol. All I want at the end of the day is to “know” it’s 30 or 40 or 50. Perfection is the enemy of the good but bad data is the enemy of all. It’s like just sort of looking at the sparkling water one day and maybe, hard to tell, not quite as sparkling the next and thinking, what is the difference and why? It still sparkles, but I’ve got the time on my hands so no reason not to wonder

 

[pookiesunshine]

i analyze a standard solution right before my pool test sample so i have a comparison. about once a month or when i have unusually high chlorine consumption.

 

[jark87]

or when i have unusually high chlorine consumption.

That’s usually my test. Even though I don’t feel like my CYA testing is anywhere near accurate, my chlorine has been holding steady for weeks, even in 100+ temps with full sun. CYA must be doing its job, as I haven’t adjusted my SWCG output since early summer.