Salinity readings on Refractometer Vs. Controller

[coralsnaked]

Yes a 3rd source would be in order to help determine what is correct. For some unexplainable reason A reef meter (NSW AT Refractometer) when calibrated to 0 w/ RODI will not be accurate at 35ppm when measuring DT water, so you must use a known source of 35 ppm to calibrate it accuratly at the point closest to what you intend on measuring. I have herd David say this over and over and Randy say there is really no good explanation. But IME what i have found to be true that is it is a given the drop of water will quickly match the temp of the meter. And further IME I have found if I calabrate my Reef Meter at 68F w/ a known source @35ppm it will be off calibration if I use the meter at say 85 F. Just saying. It ain't supposed to be that way, but it is. So what do i do? I re-calibrate my meter every few months as the ambient temperature of the house changes w/ the seasons to keep it accurate. Winter calibration is different than summer calibration.

Merry Skerry

 

[Green_Lionfish]

Hello everyone,

Thank you for your responses.

This is my update. I am getting frustrated as I can't get this solved.


So, I've been using ATC refractometer from BRS. I calibrated with their solution, which is 35ppt or 1.026. I calibrated with room temperature off 77F as the solution says.

My apex conductivity/salinity probe is brand new. I use their solution of 53,000 (53) which is also 35ppt. And I understand that it's temperature dependent. So I float the solution so it has the same temperature as the tank. Then calibrated again.

Final result:
Refractometer is 1.025 may be a little more. This is around 35ppt basically.
Apex probe is 30.9ppt. This is bascially 1.023.

Here is the chart that I've been using:
www.americanmarineusa.com/salinityconversion.html



:deadhorse1::deadhorse1:Frustrating....

 

[Hudzon]

Are you using a temp probe on the PM2 itself if not move your temp probe to it and then calibrate if they still come up the same, then adjust them both by 1 point so they both match.

 

[Green_Lionfish]

Are you using a temp probe on the PM2 itself if not move your temp probe to it and then calibrate if they still come up the same, then adjust them both by 1 point so they both match.

Yes, PM2 has both temperature and salinity probes. Are you saying I have to adjust both Refractometer and Apex by 1??? Hmmmmmmmm