accuracy of hydrometer vs refractometer

[wbrown]

Just found a possible cause for some recent losses, I bought a second IO swing arm hydrometer for keeping near my mix barrels. Did a comparison between the two, and found they were off by .08! Bought a hydrometer and neither one was closer than .04 after zeroing in with off the line ro/di water.
Spent an entire day balancing the salinity of all tanks to read the same, however I am a bit concerned with the accuracy of the refractometer.
I got one from Coralvue from a LFS as that was all that was available, and my interpretation of the Chinglish I have it zeroed. Is there another method to back-check?

BTW: anyone else notice Brightwell salt STINKS when you mix it?

 

[schwaggs]

They best option to calibrate a refractometer is to get some 35 ppt reference solution http://www.fosterandsmithaquatics.com/product/prod_display.cfm?pcatid=18718">http://www.fosterandsmithaquatics.com/product/prod_display.cfm?pcatid=18718</a>. This way you are calibrating near the range you will be measuring. However, zeroing it out with RODI is a next best solution.
[IMG]http://www.fosterandsmithaquatics.com/product/prod_display.cfm?pcatid=18718"></a>

 

[jennm]

I have the solution in the shop - we're offering to calibrate Refractometers for free this week.

Jenn

 

[jcook54]

I just had mine calibarated at my LFS yesterday and found out it was off a little. Not too much but I was using distilled water per the instructions and wasn't spot on. A refractometer is always better than a swing arm for accuracy. However, I do use a hydrometer when mixing to get the water "close" and then dial it in with my refractometer.

 

[rbredding]

I've seen the calibration solution in several shops locally..


I use RO water.. (after testing the RO water with the TDS meter)

 

[jennm]

I'd calibrated mine with RO also for years... after reading posts here, I got the 35 PPT solution - and mine was a bit off. It's worth doing with the solution. I won't do it any other way now.

Live and learn.

Jenn

 

[corigan]

I calibrated mine with ro/di and used it that way for a year. Thought it might be off and got some solution and it was spot on. Amazing. Atleast I now know that it is spot on with the reference solution.

 

[schwaggs]

JennM;465161 wrote: we're offering to calibrate Refractometers for free this week.

What a great idea!

 

[jennm]

I put that in the newsletter and in our sponsor forum.

I did have extra solution (other than the bottle in use at the shop) but Barry bought it yesterday

I'll have to reorder that, but I'll have some when I get some more if folks want their own.

Jenn

 

[jcook54]

Like ya'll I've calibrated mine with RO and grocery store distilled water for years. In fact, distilled water is what the instructions say to use. Either way, it wasn't off by all that much. Chances are good that I won't use the calibration solution all that often. Maybe once a year just to make sure. It's not like I have to make a special trip to Keen Reef to do it. I just have to remeber to take it along once in a while when I think it might be off.