Tropic Marin Precision Hydrometrer Corrections - Redux

[Randy Holmes-Farley]

Yeah, definitely a complicated process if you want to account for ALL the variables. Best of luck!

IMO, it’s desirable that someone know the details. How else can one have confidence?

 

[BeanAnimal]

That part is certainly useful! I'll start a thread at BRS to see what can be done.

I just searched for it and can’t seem to find it now either. I am traveling this afternoon but will check the bookmarks when I get back. I just looked recently when I started compiling this data.

 

[Reefahholic]

IMO, it’s desirable that someone know the details. How else can one have confidence?

You and Beananimal are the perfect two reefers to figure out all the different variables for the glass material, thermal expansion, meniscus behavior, liquid viscosity, etc. I’ll be interested to see what you guys come up with.

Following….

 

[BeanAnimal]

updates - I absolutely am unable to find the BRS table on their site. It does look like it has been removed. I did not bother with the wayback machine. So that is good. I also can't find the BRS video or two that it was linked in.

I finished the calculator as a learning experience and as a practical exercise and tool.

Tropic Marin Precision Hydrometer Correction Calculator | BeanAnimal's Reef

Use this simple calculator to temperature correct your Tropic Marin Precision Floating Hydrometer readings and never guess about your aquarium salinity again!

beananimal.com

It outputs both the direct lookup (interpolated for values not actually in the table) form the table and also the values as calculated by the accepted UNESCO and PSS-78 equations.

I did not add an option for other hydrometers... as in my search I really found none as suitable as the Tropic Marin. Most are 0.001 Sg and the TM is 0.0001

Here is my takeaway - Either the empirical table or the direct calculation will work just fine. So my calculator, Hamzas, etc. all use the same accepted equations and the output matches the table in Randy's article close enough to not matter. There are some outlier spots where the table deviates a bit and the resultant PSU is .5 to 1.0 apart (empirical vs calculated) but they are rare.

I was going to had correct the oddball spots in the table, but decided to leave it as-is and just present both the lookup value and the calculated value.

I am not an expert in this field, but am happy to try to answer questions. That said I think Randy's article covers it well enough to begin with.

Ohh and in trying to wrap my head around this mess.. I banged out a Smolov Jr. calculator too (something easier on the mind as far as logic). If you know what it is... great, if not that is fine too.

 

[taricha]

erm... I played with it a bit and am now confused

Why does your "calculated" which I think should just be from the equations of state relationship (ignoring the hydrometer) differ from this calculator that claims also to be doing the same thing....
https://reefapp.net/en/salinity-calculator

On your calculator, water that was 35.0 PSU & 1.0264 at 25C would be 1.0257 SG at 28C.

on the reefapp calculator, the water temp correction is super tiny. 1.0264/ 35.0 PSU at 25C is given as 1.0263 at 28C.

I don't know what the actual "equations of state" relationship should be here. So I don't know whose implementation is right, but I expected those to be the same?

 

[BeanAnimal]

it looks like ReefApp is more of a simple unit converter, directly converting specific gravity (SG) to salinity (PSU) and vice versa, assuming the input is already accurate for the temperature you're measuring at. So, if you enter 1.0264 at 28°C, it assumes that's a correct reading at 28°C without needing further temperature adjustment. I have no clue what the 25C column is doing, but I think it is simply working the same conversion input with a 25C device at that input.

On the other hand, my calculator compensates for the input temperature, adjusting the reading back to the reference temperature (usually 25°C). So in other words, the density is compensated for between the actual and the reference and THEN the unit conversion is done.

I hope that makes sense.