Hanna Photometer Accuracy

[alrha]

Just tested my RO/DI, my Saltwater, my Tank Water, and my Phosreactor output, and repeated them all a second time. Below are the results:

Water: 1st Test / 2nd Test
RO/DI: 0.04 / 0.06
Saltmix: 0.20 / 0.12 (Seachem Salinity)
Tank: 0.09 / 0.13
Rowaphos output: 0.11 / 0.06

Curious what others have and if their numbers jump around that much as well.
I also find it odd that my salt can be adding that much phosphates to my system. The Rowa came out higher the first time and lower the second time - makes it hard to judge if it is time to replace.

 

[rkaragozler]

I have the same problem, they say that the units have a plus-minus 3% tolerance. I have been using my unit for the past year, all i do is make sure the readings from week to week are within range of a chart of parameters.

 

[prattreef]

I also find it hard to get very consistent readings. The vials need to be super clean and I find the powder dissolves differently each test. Even in a perfect testing situation the stated +/- factor is .03 or .04 ( I can't remember which.)

 

[alrha]

I also find it hard to get very consistent readings. The vials need to be super clean and I find the powder dissolves differently each test. Even in a perfect testing situation the stated +/- factor is .03 or .04 ( I can't remember which.)

+/- 0.04

And this is our best option for testing phosphates? sheesh.

well at least i'm glad to know it's not just me.

i have yet to touch a vial by hand, always with a paper towel for fear of getting a fingerprint on it.

 

[smoq]

i have yet to touch a vial by hand, always with a paper towel for fear of getting a fingerprint on it.

Same here, vial has to be super clean before each test. I wish hanna introduce a liquid reagent, that would make life much easier. Still, I see no better option to test phosphates in tank with SPS corals.

 

[Awibrandy]

I run 3 test at a time just to be sure. Last test I ran 1st one reading was .06, 2nd. .14, 3rd. .12, so I took that to mean P04 was in the neighborhood of .13.LOL
BTW, I clean the tube with my eyeglass cloth.