My refractometer is way off when testing with Pinpoint 53mS calibration fluid

[otterpop510]

ordering the calibration solution for my refractometer now, thanks again for all the useful advice around here!..

[Randy Holmes-Farley]

here's the link to the article:


Refractometers and Salinity Measurement
http://reefkeeping.com/issues/2006-12/rhf/index.php

the contents:

General Salinity Discussion
What is the Index of Refraction?
Refractive Index and Salinity
Refractive Index and Ion Imbalances in Seawater
How a Refractometer Works
Temperature and Refractive Index: ATC
Refractometer Calibration
Imperfect Refractometer Calibration: Offset Miscalibration
Imperfect Refractometer Calibration: Slope Miscalibration
Imperfect Refractometer Use: Scale Misunderstanding and Salt Refractometers
Brix Refractometers
Clinical Refractometers
Commercial Refractometer Standards
Do-it-yourself Refractometer Standards
Tips on Selecting a Refractometer
Tips on Calibrating a Refractometer
Other Tips on Using a Refractometer
Summary

[seattlerob]

Thanks Randy for yet another great article! I just read it and noticed that I have not been waiting 30 seconds after putting the sample onto refractometer before taking the reading. I am going to try this one more time when I have a chance, to make sure my previously 'calibrated' refractometer is indeed calibrated correctly.

Before I got to that part of your article (about waiting 30 seconds), I was wondering if it made sense to bring the pinpoint solution up to the same temp as my aquarium water before calibrating (since the pinpoint solution is room temp versus aquarium water at 80 degrees). I am guessing that this is probably not a necessary step when using an ATC and waiting the 30 seconds for the temp of the liquid to stablize to the refractometer. Would you agree with that?

TIA,

rob

[Aquaduck]

I'm really curious how the automatic temperature compensation works on these refractometers. I too am guilty of not waiting 30 seconds.

Edit: OOPS. I see it is discussed in Randy's article.

[Randy Holmes-Farley]

I am guessing that this is probably not a necessary step when using an ATC and waiting the 30 seconds for the temp of the liquid to stablize to the refractometer. Would you agree with that?

Correct. The thought is that a drop on the refractometer quickly comes to the temperature of the refractometer.

I'm really curious how the automatic temperature compensation works on these refractometers.

So was I.

[Triggerfish]

also have the generic "blue unit". haven't calibrated with the test yet..but noticed that my cheapo swing arm measures .003 lower.
so likely my refrac is also donked.

[easye123]

I dont know about yall but I was taught to dip my index finger in the saltwater and tasted it to check my salinity. It works every time

..lol

[CAreefer]

I kind of hate to revive this old thread, but certainly worthy IMHO.

Word to the wise, Don't trust the RO/DI-Distilled water calibration.

My $90 captive purity ATC refractometer has really bad slope error when calibrated (per instructions) to 1.000 with distilled water.

I've had a few mysterious fish deaths of late and am currently in the throes of a moderate to severe tank wide TN event. I stay on top of parameters and they've been solid for well over a year. At the outset of the TN event I went over everything with a fine toothed comb and found nothing out of the ordinary.

I've got the same refractometer (2 yrs) and swingarm hydrometer (5 yrs) I started with. Since they both have always matched within .002 I assumed....

I figured after 2 years it was time to spring for the calibration solution. Applied 2 drops waited the obligitory 30 seconds and got a reading of 18ppt. Adjusted to 35ppt, tested tank and read 40 ppt YIKES. That would explain a few things. Tested distilled and refract read 1.009. Recalibrated to 1.000 and the entire cycle repeated again. Went out and bought one of the "better" swing arms and got a reading of 1.030. What ever my salinity is, it's too high. I'll be mixing a reference solution from the article ASAP to see where it falls on the 3 different measuring tools. This will give me something to do while I wait for my salinity monitor to arrive on Friday.

FWIW
CAReefer

[Boomer]

That is what we have been trying to tell people

[CAreefer]

So I'm a little slow on the uptake.