Milwaukee Digital Refractometer 35PSU 36PPT ???????

[Brad Wilkins]

Just invested in a new Milwaukee Digital Refractometer. I zeroed using their distilled water and then used the salt water validation solution to confirm calibration. After waiting one minute for both water and salinity solution to be the same temp and got this result 35PSU 36PPT . Aren't PSU and PPT supposed to read the same 35? Ive retested several times and finely got a result of 35ppt but now the PSU is at 34PSU.

 

[Brad Wilkins]

Disregard! I did a deep dive into this digital refractometer and it seams the PPT is and continues to be slightly off. It seems the PSU is the more accurate of the two with the Milwaukee refractometer, when they both should read the same.
It's my understanding the PPT is more likely to have that +2 accuracy as described in the manual seeing most people are getting 36ppt when using their salt water validation solution after calibrating.

 

[redfishbluefish]

No disregard! You're informing the masses of a little foible in the Milwaukee, and certainly not the first to discover this. I don't mean to blame Milwaukee, it's just the way it is with PSU versus PPT.

Salinity - PSU vs PPT​