Calibrating Refractometer

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Rmckoy

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I have a old refractometer that has always been close but always calibrated with rodi water .

since buying a Hanna salinity checker I have used it but questioned its accuracy .

can the same calibration fluid be used from Hanna to a refractometer ?
what’s the different between 35ppt Hanna calibration fluid and 35ppt refractometer calibration fluid ?
After calibrating the refractometer with the Hanna fluid , checked my tank and it was 1.030.
checked the tank and new water mixed for water change with the Hanna checker and it was 1.025
 
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Rmckoy

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The Hanna is testing conductivity, so not suitable for the refractometer which is testing the refractive index.

just make your own fluid, 3.65g table salt in 96.35g rodi you need 0.01g scales $15 from Amazon.
Is measuring conductivity as accurate as measuring reflective index ?

stability is king . But can the salinity vary at the same salinity ?
 
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I have never used the Hanna salinity checker. I have always calibrated the refractometer with 35ppt solution. I’ve heard using ro/di May be inaccurate. Do you have to calibrate the Hanna tester?
If I was to buy something else for measuring salinity it will be a bobbing hydrometer .
Same as I had 20+ years ago but apparently better quality , never needs calibrated ,

pain in the butt to measure in the rank though
 
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If I was to buy something else for measuring salinity it will be a bobbing hydrometer .
Same as I had 20+ years ago but apparently better quality , never needs calibrated ,

pain in the butt to measure in the rank though


If you are looking for stability, the refractometer is your best bet. I'm not familiar with the Hannah salinity checker. It may be great, but should be calibrated as well.

You should always calibrate with a fluid that is close to the fluid you are checking. That is why RODI water isn't recommended. It's to far from the target. @Randy Holmes-Farley has mentioned this in other posts.
 

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If I was to buy something else for measuring salinity it will be a bobbing hydrometer .
Same as I had 20+ years ago but apparently better quality , never needs calibrated ,

pain in the butt to measure in the rank though
I highly recommend the tropic Marin hydrometer, I got a glass measuring cylinder to go with mine, my tank is around 25.5c time I get 500ml of tank water in the cylinder it’s 25c, which is what the TM is calibrated to.

As for which is better, I would say it’s down to how good the device is, I thought my refractometer was solid, turns out it needs calibration every use, I check it with the TM tank water at 1.0264.
Same with conductivity, I’ve read a fair few posts on the Hanna being out.
Once you get your routine sorted with the TM it’s a joy to use, knowing you have a reliable result.
 
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