New refractometer, have some questions

[ClippersTown]

So I got this refractometer in the mail today, http://www.amazon.com/gp/product/B005ES6MOQ/ref=oh_details_o00_s00_i00?ie=UTF8&psc=1 , and I had a few questions. Why is it not recommended to calibrate with ro or rodi water? When i think about it, zeroing it out with ro water makes sense. Also, some people say use ONLY rodi water because the TDS can affect the reading... I used RO water to calibrate it, and just to test it out I put a couple of drops of tap water after calibration, and it still showed 0. using RO water to calibrate and then testing my tank salinity, I'm getting a reading of 1.031. I know this is incorrect, it should show around 1.027-1.028. Does using calibration fluid and calibrating at 1.026 really make that big of a difference? Sorry, had alot of questions. Thanks for the help!

 

[disc1]

Being as that is a saltwater and brine refrac and not a seawater refrac I'd say it is pretty important to calibrate it with a seawater equivalent. The difference in refractive index between 0 and 1.026SG is not the same for saltwater as it is for seawater.

You only get real accuracy at one point on the scale. Would you rather that point be zero or seawater?

 

[ClippersTown]

Being as that is a saltwater and brine refrac and not a seawater refrac I'd say it is pretty important to calibrate it with a seawater equivalent. The difference in refractive index between 0 and 1.026SG is not the same for saltwater as it is for seawater.

You only get real accuracy at one point on the scale. Would you rather that point be zero or seawater?

hmm, yes I understand a little bit more now. whats the difference between salt/brine water and sea water? well, i know some of the differences obviously but what is the big difference relative to the refractometer?

 

[disc1]

All the other salts that are in seawater affect its refractive index differently than pure NaCl. Keep in mind that's what a refrac measures. The numbers on the scale you see are the result of someone converting refractive index to specific gravity or salinity for you. That conversion is a little different for seawater than it is for saltwater. You can still use it, but you have to pick one point where you want it to be most accurate and calibrate to that. If you use a seawater calibrant, then your zero point may be off, but who cares. If you use rodi and the 1.026 mark is off then it throws your tank off.

 

[ClippersTown]

All the other salts that are in seawater affect its refractive index differently than pure NaCl. Keep in mind that's what a refrac measures. The numbers on the scale you see are the result of someone converting refractive index to specific gravity or salinity for you. That conversion is a little different for seawater than it is for saltwater. You can still use it, but you have to pick one point where you want it to be most accurate and calibrate to that. If you use a seawater calibrant, then your zero point may be off, but who cares. If you use rodi and the 1.026 mark is off then it throws your tank off.

oh okay i get it, so it's the conversion and the #'s difference between sea water and our home made salt water that causes the problems?

 

[disc1]

oh okay i get it, so it's the conversion and the #'s difference between sea water and our home made salt water that causes the problems?

Not seawater vs home made seawater, seawater vs saltwater.

When I say saltwater I mean JUST NaCl and water. Like taking the box of salt that you put on your food and adding it to water.

When I say seawater I mean the stuff in the ocean or the synthetic stuff that we make at home to match it but either way I mean NaCl, KCl, NaSO4, NaCO3, CaCl2, MgCl2 and all those other salts together that go into making seawater all mixed up together in water.

 

[ClippersTown]

Not seawater vs home made seawater, seawater vs saltwater.

When I say saltwater I mean JUST NaCl and water. Like taking the box of salt that you put on your food and adding it to water.

When I say seawater I mean the stuff in the ocean or the synthetic stuff that we make at home to match it but either way I mean NaCl, KCl, NaSO4, NaCO3, CaCl2, MgCl2 and all those other salts together that go into making seawater all mixed up together in water.

okay so the charts in the refractometer are for measuring saltwater, JUST the water with NaCl in it. so it's that difference in numbers on the scales between salt and seawater that messes things up