How to verify if Refractometer is correct??

[mademperor]

I just bought a Refractometer about a moth ago. It does not agree with my hydometer, or my father's hydrometer that supposedly is verified by 2 store refractometers.
How can I test if it's right, besides doing the Distilled water calibration (did that)

 

[coraljunky]

You cant verify the accuracy of a refractometer vs. a hydrometer. One is for salinity and the other for specific gravity. Neither one does both.

 

[mademperor]

okay, how can i verify Salinity

 

[coraljunky]

Originally Posted by mademperor
okay, how can i verify Salinity
Distilled water has a salinity of 0. Or you can buy calibration fluid online.

 

[scsinet]

Measure distilled water with the refractometer. It shoud read sg 1.000, salinity 0.0. If not, it's out of whack.
There are calibration solutions that can be used on refractometers, but for the accuracy that you need for an aquarium, distilled water will work fine.

 

[ifirefight]

Originally Posted by SCSInet
Measure distilled water with the refractometer. It shoud read sg 1.000, salinity 0.0. If not, it's out of whack.
There are calibration solutions that can be used on refractometers, but for the accuracy that you need for an aquarium, distilled water will work fine.
Is RO/Di water the same thing??? Could a person use this to calibrate a refractometer?? I have always wondered .

 

[salty blues]

Originally Posted by coraljunky
You cant verify the accuracy of a refractometer vs. a hydrometer. One is for salinity and the other for specific gravity. Neither one does both.
Then why does each instrument have readings for salinity & SG?

 

[coraljunky]

Originally Posted by salty blues
Then why does each instrument have readings for salinity & SG?
Ideal reference points, I believe.....

 

[salty blues]

Originally Posted by coraljunky
Ideal reference points, I believe.....
Anybody else?

 

[viper_930]

Refractometers tend to be difficult to calibrate with precise accuracy because the scales are off. If you zero a refract using ro/di or distilled water then test with the 53 ms solution your reading willl often be inaccurate. Same thing happens if you calibrate first with the 53 ms solution then test with the ro/di or distilled water. The best way to calibrate a refractometer would be to use a 35 ppt or 53 ms standardized calibration fluid because it's closest to our normal range of saltwater.

 

[acrylic51]

I'd trust a refractometer anyday over a hydrometer.....

 

[earlybird]

I use refractometer calibration fluid.

 

[scsinet]

Originally Posted by salty blues
Then why does each instrument have readings for salinity & SG?
Becuase at a certain temperature... I think it's maybe 70 degrees, salinity and specific gravity are the same. SG is temperature dependant. SG is a measure of water's density, and density of any substance changes with temperature. Salinity is a measure of the amount of salt in the water, and this wouldn't change regardless of the temperature.
Many refractometers are temperature compensating, so they will read accurately on both scales regardless of temperature.
It's ironic because even though salinity is technically the more accurate measurement, SG is what everyone uses to measure their tanks.

 

[gmann1139]

Just want to chime in that SG can be affected by other 'things' in the water. Shouldn't be enough of an effect to throw off the SG vs. salinity comparison, but it is something to consider.

 

[coachklm]

easy.... cut out the middleman..... compare yours directly to the other 2 refractometers --- then worry about calibration.