Refractometer calibration question

[tyflies]

Getting back into the hobby with a nano. Wanted a quality refractometer and got a Vee Gee. (Was tempted to get a digital checker, but went old school.)
With Brightwell calibration fluid the Vee Gee registered 1.028 out of the box. Tested the jug of salt water purchased from LFS and it registered 1.028 (they said it was 1.024).
Got a different brand of calibration fluid and Vee Gee consistently registers 1.025.

At this Point I’m roughly averaging the the two calibration fluid readings and assuming that Vee Gee sent a calibrated unit.
Any other thoughts or suggestions?

I’m filling the plate with 4-5 drops and not seeing bubbles.
Thanks

 

[Tumey]

I would decide which brand of calibration fluid you’d like to use long term then make corrections to the refractometer itself.

It’s most important to trust the fluid you’re using then get the instrument to read correctly to that calibration fluid.

 

[ChuckTownReefer]

I would go to a lfs and if they have a refractometer I would try out theres with the calibration fluid and see what's what.

 

[ChuckTownReefer]

Or just use rodi water and 0 it out.

 

[Unholy_Rigatoni]

Waiting for my vee gee to arrive so tagging along!

 

[KStatefan]

Make your own calibration fluid

 

[tyflies]

All good info. Taking it to LFS for comparison as first step.

For what it’s worth, Vee Gee instructions say to calibrate with RODI, but I thought calibrating to 1.026 was the better way to go.

 

[thewire]

Or just use rodi water and 0 it out.

If the reading supposed to be 0? If so why bother with calibration solution is just adding more confusion?

 

[Tastee]

I calibrate my Refractometer with RO however my understanding is that your reading will be more accurate if you calibrate close to the salinity target you are after. So if you are targeting 1.026 then calibrating at or close to that is going to give you a more accurate reading.

Having said that IMO stability is more important than accuracy and the error margin when calibrating with RO is small enough not to be of significance to most in this hobby. Your refractometer’s precision (ability to repeatedly give the same reading given the same testing source and conditions) is more important than accuracy. It’s more important your tank stays at a stable level of salinity than it is that the salinity level is exactly what you are targetting.