Calibrating refractometer

I just recieved my new Sybon refractometer that I purchased online which included calibration fluid.I was disappointed to find that the fluid was 0% and not the 35% that is recomended when using the unit for seawater.Even though the instructions state the the unit is calibrated at the factory and ready to use I decided to try the 0% solution and found it to be off by3% so I calibrated it accordingly.In anyones exsperience should I trust the readings I'm getting with this thing or do I need to order the right solution? I doubt that any lfs sells just the solution and will probably have to order online and pay more for shipping than the cost of the fluid,pretty disappointing.

 

Imo,yes,it will be fine.The reason calibration fluid is set at 35ppt is because,in general,any gauge typically works more accurately when calibrated in the range it's designed to be used for.Fwiw,my marine depot refractometer,is off around the same amount when calibrated with ro/di vs. the 35ppt fluid.

 

Great summary. I would get some 35 ppt solution when you get a chance, however.

 

My favorite lfs sells it,

I calibrated mine recently with a few drops of a reefing friends fluid

 

Use the 35ppt solution. Most of the time the calibration will be more accurate with the 35ppt solution.

 

LOL,yea,I meant to add that,but must have seen something shiny and got distracted.By all means,yes get the 35ptt fluid.

 

Haha

 

Some refractometers are designed to be calibrated with the fluid and some with RO water.
The one I have that calibrates with RO shows 35ppm when using the solution. In other words it doesn't matter for that one.

My BRS Refractometer clearly states:
*** Do not calibrate using RO/DI water as this will not give accurate readings***
I copy pasted that from their website.
I'm not sure why but I tried both and it is off for some reason if you use RO/DI water.
So basically it depends on the refractometer.. some are different.

 

Thanks guys,just ordered some from Bulk Reef Supply,they offer USPS shipping on small items for only $3.24.

 

Always best to calibrate at the range you are expecting to be testing in.
The two refractometers used in the hobby do differ in that the more common one is just made for testing a solution of NaCl whereas the less common, more expensive one tests seawater. The refractive index is different so if the NaCl one is calibrated at zero, there will definitely be an error in the reading at normal salt water levels.
Refractometers and Salinity Measurement
Homemade Calibration Standard