Apex test conversions wrong?

[coil1002]

When ever I add my phosphate test I use the ulr from Hannah the conversion from ppb to ppm is always wrong . I'll enter 42 ppb and it will convert it to .13 ppm when it records it. Am I incorrect in thinking 42 ppb is 0.042 ppm ?

 

[jonmos75]

No, the formula for Phosphorous is measured in ppb to Phosphate measured in ppm is:

ppb x 3.066 / 1000 = ppm
42 x 3.066 / 1000 = 0.128772 or 0.13

Here is a chart too
https://www.reef2reef.com/threads/hanna-ulr-questions.342916/#post-4268609

 

[coil1002]

Good to know its correct

 

[Sleepydoc]

I've noticed that the numbers for Salifert KH/Ca/Mg tests are off a bit if you enter the mls directly into fusion and let it convert it for you rather than entering the reading yourself. They're only off by 0.1 or so, basically with in measurement error anyway.