Refractometer

[KelliZackMOM]

I got my refractometer today. Instructions said to callibrate it with distilled water so that's what I did. My H2O tested 1.027, maybe 1.028(0.001 increments are so small). My hydrometer has been bouncing between 1.025 and 1.026 the past few days so I thought maybe it was a little high, but I knew refractometer would be coming any day so I didn't mess with the water because I haven't really been trusting the hydrometer. I've got readings anywhere from .021 to .026 even though I'm sure I had it flat and had no air bubbles in it.
Has anyone ever used a refractometer that said to callibrate with distilled? Does that sound right?

 

[JohnVH]

My refractometer says to calibrate with distilled water. I calibrate mine with my RO/DI water. If you do just make sure you get a 0 TDS reading. (Total Disolved Solids) If you do not have one you can buy them at almolst any Home Depot or Walmart for about $15.00

 

[FishyReef]

Yes, I calibrated mine with RO/DI as well. Two other things that could be affecting variation: (1) make sure to wipe off the glass in between uses so that salt doesn't dry on the prism otherwise you will get false readings, (2) double check that your refractometer takes temp into account, and if not, then make sure to follow the instructions for how to take readings at different temps, which can impact how your salinity reads.

 

[bjohanson1234]

I calibrate mine to 35ppt with calibration fluid. Mine reads both ppt and SG.

 

[KelliZackMOM]

Thanks guys, I used store bought distilled, but my RO/DI unit is also coming anyday so I'll re-callibrate it again with that and go from there and start lowering SG a little if I have to.
Glad to hear I can get a TDS monitor at store. I don't think my unit comes with one, but I was waiting until it got here to make sure before I ordered one. At least now I know I won't have to wait for something else to ship.

 

[bjohanson1234]

I rinse the lens with RO water after use instead of just wiping it down. Also, focusing the eye piece will let you see the marks better.

 

[KelliZackMOM]

I calibrate mine to 35ppt with calibration fluid. Mine reads both ppt and SG.

ppt, would that be the other column that ranges 0-100? Has %o symbol.

 

[bjohanson1234]

I doubt it. PPT stands for parts per trillion. It is not a % number. The calibration fluid is the same salinity as sea water. Most refractometers are designed for pure sodium chloride, table salt, so calibrating it at 0 of pure water introduceses a small variance since our water we make up contains other elements in it. It probably isn't a significant difference, but why not get it as close as possible.