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Old 11/02/2014, 02:50 PM   #1
Tuffloud1
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Red Sea Refractometer Problem

I purchased a Red Sea Refractometer which is different than a regular refractometer since it is calibrated to accurately read seawater unlike most others which are calibrated for brine solution.

The issue I am having is when I attempt to calibrate it with my 0 TDS water, it never stays on zero. It states to make sure the refractometer is between 72-74 degrees when calibrating, however once I get it to zero, when i come back later to make sure it's still on zero, it is above zero every time.

I am using the same exact water and the temperature is the same.

Why will this thing not stay on zero? Very frustrating.


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Old 11/02/2014, 03:30 PM   #2
outssider
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First off, you should be using a calibrated fluid at 35ppt no matter what the directions say that came with the refractometer. like this....

http://www.bulkreefsupply.com/pinpoi...n-fluid-1.html

or

http://www.bulkreefsupply.com/pinpoi...n-fluid-1.html

second, some refractometers are very temperature sensitive, so if the refractometer itself changed temperature, you will have results that change.

thirdly, if you calibrate in one type of light then recheck in a different type of light, you could have errors.....


always best to calibrate just before every use.....


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Old 11/02/2014, 09:36 PM   #3
Tuffloud1
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Quote:
Originally Posted by outssider View Post
First off, you should be using a calibrated fluid at 35ppt no matter what the directions say that came with the refractometer. like this....

http://www.bulkreefsupply.com/pinpoi...n-fluid-1.html

or

http://www.bulkreefsupply.com/pinpoi...n-fluid-1.html

second, some refractometers are very temperature sensitive, so if the refractometer itself changed temperature, you will have results that change.

thirdly, if you calibrate in one type of light then recheck in a different type of light, you could have errors.....


always best to calibrate just before every use.....
Okay, I will try only calibrating using the solution despite the instructions.

Another thing that is confusing me is some will say 35 ppt equals 1.025 and others say 35 ppt equals 1.026. Yet when I do a salinity conversion using the online calculators, 1.025 will convert to 33.2 ppt. I don't get it.


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Old 11/03/2014, 10:37 AM   #4
disc1
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Are you doing that conversion for saltwater or seawater?


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Old 11/04/2014, 05:57 PM   #5
outssider
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on my refractometer I have the 35ppt on one side of the scale corresponding to 1.0265 (approx.) on the other


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