i bought a Salinity Refractometer and.....

i did calibration with pure water.

Then, i melted 3 grams of salt mix in 97 grams of warm enough fresh water. It may be around 30 ppt in common knowledge but my new refractometer showed 25ppt.

after that i tried measuring again with same solution but little bit cold and
refractometer showed 20ppt.

i checked up salinity with pure water several time to calibrate
but it works very well with pure water.
my refractometer has ATC and i used Ocean Pure salt mix.

What is the problem with me?
Salinity Refractometer? Salt mix? or My Idea about ppt?

Actually i dumped up my 60gals tank since my first fishes were gone at once with unknow problems so I strongly doubt the salt mix.

 

my BRS refractometer came with its own calibration fluid and calibrates to 1.026...sounds like maybe you didnt get the calibration fluid or need to purchase the fluid separate to calibrate?

 

Mine is calibrated with just distilled water

 

When you calibrate with ro/di or distilled you get an error due to the instrument most likely being a NaCl refractomter not a NSW refractometer. You need calibration fluid if you want to be accurate.

 

As mentioned, if you have a salt water (NaCl)one, it will give your errors at normal salt levels for our aquariums. Water that is actually 1.0264 will read 1.024, nothing like the errors you are seeing.
The accuracy of your measuring equipment would be suspect in your present problems. Most people don't have scales to accurately determine 3 grams, as it should be accurate to +-.01 to get a solution reasonably close.
If you have a seawater refractometer you shouldn't have any error to speak of.
See Randy Holmes-Farley's information:

Refractometers and Salinity Measurement by Randy Holmes-Farley - Reefkeeping.com

Reef Aquarium Salinity: Homemade Calibration Standards by Randy Holmes-Farley - Reefkeeping.com

 

Thanks for comment, Guys,

i meant i did calibration with distilled water but it was not good for calibration?
actually i've thought calibration fluid was dsitilled water but i was wrong.


Thanks Rayjay for good informations.

 

Pure water is not good to calibrate. You would be Calibrating to the low end of the scale. You need to get calibration fluid and calibrate at the lvl you are wanting to read at.

 

If you had a seawater refractometer you could calibrate with distilled water.
If you have the much more common to the hobby salt water refractometer then it is best to calibrate with the standard. Or you could just keep note of the fact that if you want 1.0264, then go by 1.024 on your refractometer.
That being said, if you happen to be needing to do hyposalinity at any time, it will be more accurate to use the water to calibrate with at that time for reading around the 1.009 level.

 

You could go over to a friends and check their salinity on their refractometer and then calibrate yours that way.

 

Problem with that is that you don't know if the other refractometer has been calibrated correctly.
There are a lot of people who THINK theirs have been done correctly and are producing accurate readings, but not all are.