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Calibrating Refractometer

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I used the 1.026 water (I got from the BAR hobbyist event) and also double checked with RO/DI water and adjusted the top screw to calibrate my meter...

After a few days I was shocked to see salinity spike and after checking with std solution, reading was again off (had to re-calibrate).

This happened to me a few times where I first had to calibrate before I take any reading.

Is this normal? How frequently do you calibrate? Am I missing a step after calibration (why is it not holding to that adjustment).

Thanks for any advise.
 
IMO, it should hold unless that calibration screw is very loose, after some 5-6 years mine was off 0.001.

FYI don't use RO/DI water to adjust nor check the calibration, unless you're extremely lucky and have the same response slope for 1.026 as you do for 1.000 you'll have a slope error.

Here's a rather long read on errors if you're so inclined
http://reefkeeping.com/issues/2006-12/rhf/index.php

Here's another if you ever want to make your own calibration solution
http://reefkeeping.com/issues/2004-06/rhf/index.php
 
I just received my refractometer in the mail yesterday which came with the 1.026 calibration fluid. There was a sticker on the case that warned not to calibrate using RO/DI water. That only calibration fluid should be used otherwise a false reading would be given.

I have never used a refractometer before, it is fun to use. :)
 
You should not need to recalibrate much. I have probably done it twice in 10 years.

Do you always have to fix calibration the same direction? If so, probably a loose or broken screw.

Note that temperature can be an issue, although rare.
Usually only if refractometer is stored in a cold garage, and you measure warm water.
(Temperature compensation fails)
But in that case, you would be adjusting it back and forth.
To avoid, let refractometer, calibration water, and tank sample set inside house for a bit.
 
My screw is tight enough that I have to apply some pressure to make the adjustments.

Dumb question: what's the outer right for (that houses the small adjustment screw)?

I'm going to do some more tests today and will post back here.
 
I hadn't calibrated mine in years and it was still bang on.
One thing to watch for is that you're getting enough water to cover the entire viewing window. Also, when you're done using it, wipe it down with a damp cloth to clean off any residue. A dirty viewing window can build up salt and change your readings.
 
I tested today and the readings were off again :( and I noticed the adjustment screw not so tight (it's not loose too).

What's my best bet to get it tight?
 
If you got it recently and have prime just return it and get a new one. Sounds like it's defective.

Sent from my Nexus 5 using Tapatalk
 
Navdeep said:
Dumb question: what's the outer right for (that houses the small adjustment screw)?
Click to expand...


Assuming you meant 'ring' not 'right', that is the lock ring. Loosen it, make adjustments, tighten the ring then check adjustment. Repeat as necessary till it's spot on.

It's also important not to have any bubbles in the sample. Don't drop the cover down on the sample, lower it slooooowly. If there are small bubbles, lift it and try again.
 
Yea I meant ring... And all this time I've just been adjusting the inner screw.

So the way to do it is to loosen the outer ring, adjust the inner screw and tighten the outer ring?
 
Navdeep said:
Yea I meant ring... And all this time I've just been adjusting the inner screw.

So the way to do it is to loosen the outer ring, adjust the inner screw and tighten the outer ring?
Click to expand...


Yep. Don't forget to check and adjust as needed after the ring tightening. Sometimes the adjustment moves.
 
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I've been pretty lucky with mine so far. Seems to hold its calibration. I got mine from Neptunes.


Sent from my iPhone using Tapatalk.
 
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