Are You Properly Calibrating Your Refractometer?

[shiftline]

Are you properly calibrating your refractometer?
Lot of people just use RO/DI water which will read 0..however your not going to get the the most accurate results.

the next batch of people will use proper 35ppt/1.026 calibration solution which gets you closer.. but ar you taking into account the temperature compensation?

 

[BIGSHOW]

Good Vid. I know this has been discussed a number of times on this forum, but the best info I found is below


www.reefkeeping.com/issues/2006-12/rhf/index.php

 

[Janice]

Thank you for this. We just followed the instructions that came with ours and it did not say anything about calibration solution.

 

[Pistol]

Calibration fluid is not perfect, it's SG rises as it evaporates. I have 3 bottles of 1.026 calibration fluid and only 1 reads 1.026.
I have a Sybon and a Milwaukee digital, the milwaukee an only calibrated with RODI and when I calibrate my Sybon with RODI it reads the 3 fluids I have the same as the Milwaukee, they both have temperature compensation and it works. After hours of testing these things at different temperatures and calibrating methods I have concluded it is best to use RODI to calibrate and allow 15 seconds for the temperature to be compensated.

 

[Janice]

Interesting. Thanks for that.

 

[Pistol]

Actually my tap water reads the same as my RODI water, 0.000, your RODI water will always have a SG of 0.000, guaranteed, your 1.026 calibration fluid will always be questionable, guaranteed.

 

[TORX]

Exactly, that is my opinion as well. That is why when you set up your pH you use 2 calibration fluids to do the proper range. Just because the lower is set up, it does not mean the higher is right. I need some calibration fluid. I think I might bring it and offer calibrations at Brantford Coral Show.

 

[Pistol]

I think you misinterpreted my last post, I corrected the wording, what I'm trying to say is that you cannot trust the calibration fluid to be accurate.

 

[TORX]

True enough. Who calibrated the calibration fluid? Lol

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[Nonuser]

True enough. Who calibrated the calibration fluid? Lol

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Thanks, now I'm having a existential crisis

 

[Pistol]

The last bottle I bought was this http://www.bulkreefsupply.com/aqua-craft-refractometer-calibration-fluid.html
I read 1.028 on both my refractometers, so I took it to London Frag Fest and had about 10 vendors test it with their refractometers and every one of them read it as 1.028
Like I said, I now have 3 bottles by 3 different manufacturers and one is 1.025, one is 1.026 and the newest one is 1.028 which I know for a fact is 1.028.
RODI water is guaranteed to be 0.000 and who really cares if the refractometer is off by 0.0001 pt at 1.026, it's more important to be consistent.

 

[shiftline]

I actually have 2 bottles of calibration fluid and there is a slight difference (maybe .001) off so your right on not always trusting them (especially if you dont tighten the cap enough!)

Calibrating it to 0.. will make it more accurate in the low end.. calibrating with 1.026 /35ppt will make it more accurate at the high end.. you "can" calibrate with either but its always best to calibrate to the range you are trying to test

Throwing the calibration solution in the fridge for 2 min then testing dropped the reading but about 2 points so temperature of the sample can also sway the results.

 

[Pistol]

I actually have 2 bottles of calibration fluid and there is a slight difference (maybe .001) off so your right on not always trusting them (especially if you dont tighten the cap enough!)

Calibrating it to 0.. will make it more accurate in the low end.. calibrating with 1.026 /35ppt will make it more accurate at the high end.. you "can" calibrate with either but its always best to calibrate to the range you are trying to test

Throwing the calibration solution in the fridge for 2 min then testing dropped the reading but about 2 points so temperature of the sample can also sway the results.

If I calibrate mine to 0 my tank reads 1.026, if I calibrate it with my 1.026 solution my tank reads 1.026, so I don't believe the calibration theory, it must have been started by somebody or company selling calibration fluid. The refractometer is not a pH probe, it's a mechanical device and does not need to be calibrated like a pH probe.

 

[Nonuser]

Where do they sell the solution? I have read you can DIY the caliberation solution has and one done this and if so how was it?

 

[shiftline]

Most online reef stores sell the bottles for about $5. I think I got mine form JL aquatics


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[Pistol]

rodi is your best calibration solution, to any body with solution, calibrate to refractometer with tap water and check it with your solution, unless your tap water has super high tds it read ban on so using rodi guarantees 0 sg. The solutions just add another variable for error as they are not manufactured to perfect tolerances for the hobby market.

 

[Nonuser]

rodi is your best calibration solution, to any body with solution, calibrate to refractometer with tap water and check it with your solution, unless your tap water has super high tds it read ban on so using rodi guarantees 0 sg. The solutions just add another variable for error as they are not manufactured to perfect tolerances for the hobby market.

Well I read this post and thought about the last time I calibrated the meter and I honestly couldn't remember.
I grabbed the bottle of calibration fluid to do the test and bam it was empty! Most stores are closed Monday Tuesday so I was thinking about hitting The Coral reef shop tomorrow, they should have it. The RO unit needs some maintenance the tds is 8-9. I have no idea what component needs replacing? resin, carbon, membrane....

 

[Pistol]

tds of will have a sg of 0

 

[shiftline]

True that! And your best option if you don't have calibration solution


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