calibrate refractometer

[moovinfast]

Can I do it just using RO/DI water?

[ThePremiumAquarium]

Yes, I try and make sure the water is roughly at the same temp as your tank water and make sure your TDS is at 0.

 

 

Garrett

[impur]

I would suggest using a known SG solution to calibrate your refractometer unless it is a higher quality/lab grade refractometer.

 

My refractometer was about 3ppt off using RO water. Its one of the common $40-50 ones.

 

http://reefkeeping.com/issues/2006-12/rhf/index.php#11

 

 

 

"Refractometers can lead to incorrect readings in additional ways and, again, these issues abound for reef aquarists. One is that many refractometers are intended to measure sodium chloride solutions, not seawater. These are often called salt or brine refractometers. Despite the scale reading in ppt (‰) or specific gravity, they are not intended to be used for seawater. Unfortunately, many refractometers used by aquarists fall into this category. In fact, very few refractometers used by hobbyists are true seawater refractometers.

 

Fortunately for aquarists, the differences between a salt refractometer and a seawater refractometer are not too large. A 35 ppt sodium chloride solution (3.5 weight percent sodium chloride in water) has the same refractive index as a 33.3 ppt seawater solution, so the error in using a perfectly calibrated salt refractometer is about 1.7 ppt, or 5% of the total salinity. This error is significant, in my opinion, but not usually enough to cause a reef aquarium to fail, assuming the aquarist has targeted an appropriate salinity in the first place. Figure 23 shows the relationship between a perfectly calibrated and accurate salt refractometer and a perfectly calibrated and accurate seawater refractometer when the units are reported in salinity. This figure shows the measured salinity reading for seawater being about 1.7 ppt higher than it really is."

[Smann]

I would use what the manufacture reccomends in the instructions included, if you dont have them they can probably be found online.

I skimmed thru the above mentioned article to find the results (the last time this came up) and came across his recipe for making your own solution. Use a 2 liter coke bottle for a measuring device??, how full is a 2 liter bottle when you buy it? is it marked?. If he is shooting for complete accuracy why not use a 2 liter water pitcher thats marked, how much is the salinity going to be off if not mixed correctly

I would (and I do) find and follow the manufacturers instructions

[Nate213]

I would use what the manufacture reccomends in the instructions included, if you dont have them they can probably be found online.

I skimmed thru the above mentioned article to find the results (the last time this came up) and came across his recipe for making your own solution. Use a 2 liter coke bottle for a measuring device??, how full is a 2 liter bottle when you buy it? is it marked?. If he is shooting for complete accuracy why not use a 2 liter water pitcher thats marked, how much is the salinity going to be off if not mixed correctly

I would (and I do) find and follow the manufacturers instructions

 

X2. Im glad I wasn't the only one that noticed that. I agree with the article, but the method is flawed. You can only be as accurate as the measurement device with the largest tolerance. Every measuring device has an accuracy tolerance. To homebrew a calibration sample, you need to have lab grade equipment to measure out the correct quantities. Otherwise you are just wasting your time. A refractometer is a huge step in the right direction. Swing arm hydrometers are garbage. I think the key is to be consistent and stable. People still argue with the 1.023 to 1.027 range for Specific gravity. Some like it higher, others dont. Either way if you end up in that range, your stock should be healthy.