CYA standard solution test result 2

[Torrente]

Coinciding with a new order of some reagents I have ordered too a 50ppm CYA standard solution from TFTestkits, the results are pretty much the same as last time. I can see quite clearly the dot at 50PPM and at 40PPM I can feel that it is there.
In any case this s useful to me as I am able to calibrate my measure, I think that I am able to repeat the test consistently to see the dot like in this 40PPM and I will add 10PPM to the measured result.

I did something similar time ago: CYA standard solution test result, can I extrapolate?

 

[Katodude]

Following this thread since measuring CYA constantly gives me fits. Going to order standard solution with my next TF refill order.

Does anyone shake the tube after you pour in the solution to the desired level? When I do that the dot seems to obscure more for a few seconds. Or is looking at the dot that soon after shaking contra indicated?

 

[Bvacchiano]

Now just make sure u do the actual pool CYA test at the exact time of day, with exact lighting, and in same position! Basically duplicate what you are doing 100% to make sure it’s done right.

 

[JoyfulNoise]

I've never liked that round tube. The Taylor #9056 or #9058 comparator block uses a square cross section vial that is purposefully frosted to create as much diffuse lighting as possible. Also, because the #9056 block has the larger pH comparator connected to it, you can hold that side of the block so that your hands are no where near the CYA side of the tube. If you are testing the way you are holding that tube in the picture, then you're doing it slightly wrong. Your fingers should not block the incoming light into the tube in any way. So with that tube you need to hold it at the top of the cylinder by pinching it between two fingers and keeping the rest off your hand from blocking the light in anyway. You should also be testing out in high noon day sun with the tube held waist high in the shadow of your body.

No matter what, the test only has an accuracy of about +/- 15ppm but is the cheapest and simplest way to make a residential CYA tester.

 

[Torrente]

If you are testing the way you are holding that tube in the picture, then you're doing it slightly wrong. Your fingers should not block the incoming light into the tube in any way. So with that tube you need to hold it at the top of the cylinder by pinching it between two fingers and keeping the rest off your hand from blocking the light in anyway. You should also be testing out in high noon day sun with the tube held waist high in the shadow of your body.

Thank you for your answer. The important thing is that I am able to calibrate myself with this and as you say it seems that it is not precise anyway.
I usually do it like that, fingers on the top. Regarding time I usually do it in the morning, as I live near the equator if I do it at noon I will not have any shadow most of the year.