Salinity Percentage in PPT vs Specific Gravity: Which is Most Accurate

Adamantium · Jan 9, 2019

Hi all!

I think I already figured out the answer, but I wanted to hear your opinions.

I just got the HI 98319, and it measures SG to the thousandths (1.026), and salt PPT to the hundredths (35.2).

Is it therefor most accurate if I keep it at PPT? It seems like that would be the case, but I wanted to confirm.

Thanks!

PS: I already freaking love this thing. Great buy at $69.

Adamantium · Jan 9, 2019

Oh, wait... Looking at their Accuracy Specifications, it's only accurate to 1 PPT... That's a pretty big range. SG is accurate to .001. See below:

±1 ppt for 0.0 to 40.0 ppt; ±2 ppt for readings over 40.0 ppt

±1 PSU for 0.0 to 40.0 PSU ; ±2 PSU for readings over 40.0 PSU

±0.001 S.G.

±0.5°C; 1°F

EMeyer · Jan 9, 2019

Umm... 0.001 units of SG is equivelent to 1 ppt.

Specific gravity makes no sense whatsoever as a unit for salinity, and I'll never understand why the hobby has adopted it while all marine science research uses PPT or PSU. In any case, the units you choose to report don't affect the precision of the instrument.

Adamantium · Jan 9, 2019

EMeyer said:
Umm... 0.001 units of SG is equivelent to 1 ppt.

Specific gravity makes no sense whatsoever as a unit for salinity, and I'll never understand why the hobby has adopted it while all marine science research uses PPT or PSU. In any case, the units you choose to report don't affect the precision of the instrument.

I’m sure you’re right, but I’m not certain I follow. Isn’t 35 vs 36 ppt the difference between 1.0264 and 1.0271?

Am I misinterpreting something here?

The reason I ask is because I'm trying to get a reading of 1.0265, but the device can only read out to 1.026.

35.1 PPT is 1.0265, but now I'm seeing that it could be off by as much as 1 PPT, which seems like it's in fact, a bigger range than the SG reading.