How do I calculate a Specific Gravity value when using PM2 / Salinity module with temperature compensation enabled.

[Tim.Kelley]

How do I calculate a Specific Gravity value when using PM2 / Salinity module with temperature compensation enabled?


I have a PM2 / Salinity module connected to my Apex System.


I have both a salinity (conductivity) probe and a temperature probe connected to my PM2 module.


I have Temperature compensation enabled and have set the value to 2.2 which I believe is recommended


in the PM2 User Manual. So I believe the Salinity value that gets displayed on the screen is already taking into


consideration the temperature. So then my question is how do I calculate a Specific Gravity value from


the salinity value ( in ppt )shown on my display.

[zombie]

1.025 is approximately 35 ppt. It's actually better to just get used to the salinity system then try to convert and just aim for about 35 ppt.

[1983evansd]

I believe 34 is 1.025 and 36 is 1.026


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[zombie]

I believe 34 is 1.025 and 36 is 1.026


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It depends on the Mg content in your water, which is why I don't even bother with SG anymore. Too many variables to figure out how much salt is actually in the water. ppt separates the two.

[Tim.Kelley]

I sent an email to Neptune Systems Support and asked them my original question as posted in this thread.

They recommended I use this website.

http://www.saltyzoo.com/SaltyCalcs/SgPptConv.php

So at least for now I'm going to go with that one.

I googled salinity conversion charts and there must be at least 10 of them and they all mostly give different values.

SaltyZoo says 1.025 Specific Gravity is 33.2 ppt

I also checked this website http://www.reefs.org/library/salinity.html





It says 1.025 Specific Gravity is 35.8 ppt (at 80F, My tank runs at 80F)

which chart is correct?

Wish I had a Masters degree in Chemistry!