Refractometer calibration

[Hondatek]

Can you use tap water or does it have to be distilled or ro water?

 

[mfdrookie516]

Everything I've read says you need to calibrate to 35ppt, that using ro/di or distilled is not an accurate way to calibrate.

 

[Hondatek]

Hmm that's what the instructions say . That's rather odd

 

[ccCapt]

Everything I've read says you need to calibrate to 35ppt, that using ro/di or distilled is not an accurate way to calibrate.

That is the proper way to calibrate a refractometer.
A refractometer measure how water bends (refracts) light. Freshwater bends light differently than saltwater so if you calibrate only using freshwater you don't know for sure it will give an exact reading when using saltwater. It should be calibrated with a saltwater solution of a known salinity...which is what calibration fluid is.

 

[Hondatek]

Are they all calibrated the same then? The instructions say to use distilled water and adjust the screw untill the blue area is at 1.00 . It's an auto temp adjusting from marine depot . Maybe this one works different?

 

[ccCapt]

Nope. They are all the same.

 

[Hondatek]

I don't get it then why do the instructions say to do that?

 

[ccCapt]

Refractometer for reading salinity w/ Free Calibration fluid - English
Steps to calibrate your unit

• 1) Using the dropper place a few drops of the solution on the glass and close the lid.
• 2) Looking through the unit and turn the screw until the unit reads sg 1.026 (35ppt)
• 3) Screw the cap back on your calibration solution for storage. It is important that the cap is on tight or water will evaporate ruin the solution.

*** Do not calibrate using RO/DI water as this will not give accurate readings***​

 

[Hondatek]

Ok im going to call marine depot and get to the bottom of this .

 

[Hondatek]

Just got off the phone with marine depot. He said ro di or distilled water is how it's supposed to be done but he also said you can do it with calibration fluid but the difference will be minuscule .

 

[FTMMWS]

I would use the calibration fluid ,,that way it is exact

 

[Hondatek]

I'll still try to get some and see how much it changes. It was double checked at my Lfs with a digital refractometer so it should be acurate

 

[FTMMWS]

I'll still try to get some and see how much it changes. It was double checked at my Lfs with a digital refractometer so it should be acurate

Then it should be good

 

[ccCapt]

Calibrated with RO only will be close and probably be about 2ppt off from being calibrated with calibration fluid.