I have no idea what my salinity truly is. Please help.

[MuscleBobBuffPants]

Testing a refractometer with rodi tells you almost nothing. They can be off significantly at 35ppt and still read 0 at 0 (or read zero at 10 PPT). Calibration solution is like $8 for a big bottle.


Refractometers get used for things that need way more precision than a reef tank does. Calibrate it (at 35 PPT!)regularly. Use it. Don't worry too much.

I guess I should just stop using the Hannah checkers then. focus on consistent 35 ppt with the refractometer

 

[Cmooreinor]

I guess I should just stop using the Hannah checkers then. focus on consistent 35 ppt with the refractometer

So I am dealing with this as well.... my Hannah is showing right at 35ppt.... refractometer closer to 38ppt. And that is calibrated with solution refractometer. Not sure what to trust...... I am guessing the solution calibrated refractometer....

 

[Crashnt24]

I use the Milwaukee digital refractometer. It pretty much was spot on with my old swing arm hydrometer. So I just stick with one instrument and keep consistency. As long as your average for all your testing methods aren't at dangerous levels, pick one and stick with it. Good luck!

 

[Rjukan]

I'm curious, have any of you used your testers to check your RODI water at the same time? I know it's all about the calibration fluid, but just to see if you get 0.0 for RODI...

 

[Pistondog]

Just stating the obvious, all the hannas are colorimeters and thus subject to inaccuracy if dirty. We must all dry the vials before insertion, even for the zeroing 'C2' step.
Otherwise the color sensor may be inaccurate.

 

[Pistondog]

I use the Milwaukee digital refractometer. It pretty much was spot on with my old swing arm hydrometer. So I just stick with one instrument and keep consistency. As long as your average for all your testing methods aren't at dangerous levels, pick one and stick with it. Good luck!

The Milwaukees are very convenient. Do you zero yours with distilled water regularly? Mine was off, so zero.
Do you find it accurate over wide ambient, say 70 to 90. Thats where I ran into problems

 

[Crashnt24]

The Milwaukees are very convenient. Do you zero yours with distilled water regularly? Mine was off, so zero.
Do you find it accurate over wide ambient, say 70 to 90. Thats where I ran into problems

I zero mine before every single test. Also, I let the liquid sit in the well for 15 seconds before pressing "read". That way it has time to adjust the temp. I find it very accurate after taking those steps.

 

[92Miata]

I'm curious, have any of you used your testers to check your RODI water at the same time? I know it's all about the calibration fluid, but just to see if you get 0.0 for RODI...

Getting 0 testing RODI tells you nothing positive about the meter. A meter can be 0 at 0 and off by 20 PPT at 35ppt.

Calibration at 0 almost always makes your meter less accurate at 35 ppt

 

[Rjukan]

Getting 0 testing RODI tells you nothing positive about the meter. A meter can be 0 at 0 and off by 20 PPT at 35ppt.

Calibration at 0 almost always makes your meter less accurate at 35 ppt

I never said calibration to 0 RODI...

I also don't agree that checking RODI after using a calibration fluid to set a meter tells you nothing. I like to see a baseline check to another known value before testing the SW to see the tester working properly.

 

[92Miata]

I never said calibration to 0 RODI...

I also don't agree that checking RODI after using a calibration fluid to set a meter tells you nothing. I like to see a baseline check to another known value before testing the SW to see the tester working properly.

Again, it doesn't give you any sort of baseline. Showing 0 on RODI doesn't tell you that the meter is working correctly, and matching up on one known value doesn't tell you anything about other values. "Broken clock" and all.


I've seen crappy refractometers read 0 on RODI and read 1.050 on 1.026 reference solution. 0-at-0 is utterly meaningless. It doesn't tell you that the slope is right, and it doesn't tell you that the offset is right. It's false security.

Spend the $5 and buy a bottle of reference solution. Or use a gram scale and make some.

RODI can tell you nothing useful about your refractometer. It's like saying "my speedometer is accurate because it reads 0 when the car is parked"