Refractometer calibration ?

I got the $44.95 refractometer from Dr. Fosters and I need to calibrate but I have questions. Here is what I did:

1. I took a cup of my RO/DI water but the temp was 63 degrees. So I place the cup in the sink and filled around the cup with warm water to bring it to 77 degrees.
2. After temp was 77 I place a big drop on the lens and looked into the refractometer. It was reading a little above 1.000 so I adjusted the calibration screw until it was 1.000.
3. I re-tested several times and got the same results.

The question is, did I do it right? Thanks...Jeff

 

Adjust to zero as opposed to 1.0000

 

It has 0 on one side and 1.000 on the other. Did the rest of the process sound good? Thanks...Jeff

 

I believe that is the correct way to calibrate....

Anyone know if there is a difference between calibrating with RODI vs distilled. My refractometer specifically says to calibrate using distilled water.

 

Rodi could still have small amounts of tds in it vs distilled which should have none. I don't know if there is enough to make a difference in calibrating but I use ro water and not distilled as I believe that consistency is more important than the actual value except if doing hyposalinity to treat ich.

 

Sounds right to me.

 

That is the way that I have done it before and it works. They also make a salinity solution that you can calibrate your refractometer. I think you calibrate it with the solution at 35 ppt. It is my understand that it is more accurate because it is closer to the numbers that we are normally looking at. I don't know if it makes that much of a difference, but I am sure others on here will.

Ivy

 

This is because most of the refractometers sold to hobbyists are not calibrated for NSW.....they are calibrated for NaCl (Sodium Chloride) only. Since NSW or ASW has more ions in it than only NaCl they are off brand new right out of the box if you calibrate to zero with distilled water.

However, Mocarski makes a good point.

I personally like to have mine spot on and that's why I use calibration fluid at 35 ppt. However, most people have been using refracts for years not even knowing their readings are wrong. At least a refract is consistently off unlike hydrometers.

 

Yeah, I originally did the same thing as you, but then was told to use calibration solution (the solution I bought was at SG 1.0265). When I did that, I realized that my prior calibration with RO/DI was slightly off. So I'd recommend a calibration solution, if possible.

 

I dont mean to steal the thread but I was wondering....Since I was sent this bottle of calibration fluid, about how often do I need to actually calibrate the refractometer? Every time I test or is that one initial time enough?