Where to puchase standards solutions

[GaryT58]

Measurement Systems Analysis, a six sigma tool to verify that an instrument is correct within your expected tolerances.

Basically you have a few people run the tests on the same samples and plug those values into a sigma calculator like Minitab. The results are statistically corrected so you can tell if your measurement system is good enough. For example, you buy the standard and your 50 ppm solution shows 42. How do you know that you didnt affect the results by misreading or poor technique? Or, you get 50 and say your tester is perfect, again how do you know you tested correctly? A MSA takes all of the factors into account and "normalizes" them.

Engineering geek stuff, but very useful.

Thanks for the info. In essence I want the standards so I can test the accuracy of my device and my test method. My device is pretty simple - fill sample, add drops of reagent, mix, put in device which reads and displays results. With the standards I would like to see the variance (deviation) in multiple tests and see if this is acceptable (to me).

I am surprised I am not able to find some reviews of pool testers that quantitatively compares them using NIST standards. But maybe its the engineer/science background in me that wants that level of verification.