So I was double checking my Apex salinity probe today and my Hanna salinity tester. I first calibrated the Hanna against its reference packet of 35ppt, then I calibrated my Apex probe against the Neptune 53,000 calibration solution. Both tested properly against their respective solutions at 35ppt. However when I tested my tank they were different, so I tested the Neptune calibration solution with the Hanna and it came up as 33.1ppt. This would explain the difference I’ve been seeing between my Apex and Hanna but this whole time I was assuming the Apex probe drifted. Now that I know the reference solutions don’t test the same I broke out my refractometer and it was closer to the Apex probe than the Hanna so I’m trusting that for now.
Has anyone else seen this difference with the reference solutions? Is there a reason they don’t line up at 35ppt? Which one should I trust considering they are both accurate to their respective reference?
Has anyone else seen this difference with the reference solutions? Is there a reason they don’t line up at 35ppt? Which one should I trust considering they are both accurate to their respective reference?
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