refractometer calibration standard is off, how do we know whats real?

[FernBluffReef]

Used my refractormeter a handful of times. Never had one 20 some odd years ago. I found it to be useless. Always off, hard to read - small lines so close together can’t be more accurate than +/- .002 sg. Whenever I used had to recalibrate. Maybe it’s my eyes.

And so it sits and I go back to my inexpensive instant ocean hydrometer which remains consistent and reliable and spec says to +/- .001 sg. (when used correctly which I see as a key point for many things especially reef test kits LoL) ICP agrees with my Instant Ocean. Refracto agrees when calibrated assuming I can trust and am not just wanting it make it agree. Etc.

Lately I’m using a Hanna salinity checker but I use my reliable instant ocean hydrometer to check it for accuracy every few weeks. Hanna is always a bit low.

 

[BriDroid]

Used my refractormeter a handful of times. Never had one 20 some odd years ago. I found it to be useless. Always off, hard to read - small lines so close together can’t be more accurate than +/- .002 sg. Whenever I used had to recalibrate. Maybe it’s my eyes.

And so it sits and I go back to my inexpensive instant ocean hydrometer which remains consistent and reliable and spec says to +/- .001 sg. (when used correctly which I see as a key point for many things especially reef test kits LoL) ICP agrees with my Instant Ocean. Refracto agrees when calibrated assuming I can trust and am not just wanting it make it agree. Etc.

Lately I’m using a Hanna salinity checker but I use my reliable instant ocean hydrometer to check it for accuracy every few weeks. Hanna is always a bit low.

Can the Hanna be calibrated? I have an Ice Cap, and I mixed up some of Randy’s calibration solution and try to keep it calibrated, or at least check it against the 35ppt solution often. It’s really accurate.

I agree on the Refractometer. I can’t see it lol. I had to remove the rubber eye piece to help some, but it’s so hard for my old blind self to see.

 

[JayM]

Out of pure curiosity, if you test a batch of fresh saltwater with a trusted standard and it is at the desired salinity, is there any reason that you couldn’t keep some of that water in an appropriate container and use it as a standard/calibration fluid?

 

[FernBluffReef]

Can the Hanna be calibrated? I have an Ice Cap, and I mixed up some of Randy’s calibration solution and try to keep it calibrated, or at least check it against the 35ppt solution often. It’s really accurate.

I agree on the Refractometer. I can’t see it lol. I had to remove the rubber eye piece to help some, but it’s so hard for my old blind self to see.

Yes the Hanna is recommended to be calibrated once a month. They have their own 35ppt calibration solution as it conductivity. I still find it to read a bit low. The ppt accuracy is +/-1 and the sg accuracy is stated at +/- .001. So i use sg and find it to be closer. It’s relatively quick, reads temp at the same time and quick to rinse hence why I use it for routine.

 

[Linlox]

Out of pure curiosity, if you test a batch of fresh saltwater with a trusted standard and it is at the desired salinity, is there any reason that you couldn’t keep some of that water in an appropriate container and use it as a standard/calibration fluid?

Depending on the saltwater mix used, the organics in it, evaporation rate, and its shelf stability, maybe? The maybe part makes me apprehensive and if I am testing it with a trusted standard already, will probably just use the trusted standard. Which will be Randy's DIY by weight with the hydrometer. Will calibrate my refractometers to my hydrometer for quick references.

or something like this device for S.G. that I played with.
https://www.reef2reef.com/threads/p...r-measuring-density-specific-gravity.1066348/

Read through this and will probably attempt it at some point, and suprised it didn't come up in my earlier searches. My search capabilities must be diminishing with age.

Ordered a 500ml graduated cylinder for using my hydrometer in. It just makes it so easy.

 

[chrisriker]

I had been thinking about this somewhat recently; is this a good case for ditching spyglass refractometers and just swapping wholesale to the milwaukee digital refractometers? Since you calibrate it with RO/DI water instead of a calibration solution, and we KNOW how to reliably make and measure that, it should be more accurate than a spyglass refractometer calibrated with a potentially incorrect calibration solution, no?

 

[BeanAnimal]

IMHO the milwaukee pruduct is absolute trash. On Its best day it is +/-2 PSU

So if it reads 35, it could be anywhere between 33 and 37....

... if reads 33... you could be anywhere between 31 and 35

And that is if it actually calibrates properly.

it is an expensive toy.

 

[chrisriker]

That's not much more than a handheld spyglass refractometer, no?

 

[Tamberav]

My VeeGee $$$ refractometer says to calibrate with distilled (or RODI works) in the instructions.

It never drifts... like ever.. so I suppose if you use other methods to double check and get it dialed in, it should work without ticking you off like the cheap ones.

VeeGee claims +/-1 ppt

My understanding is the cheap refractometers are for Brine and VeeGee is for Seawater.

BUT... I would think calibrating with accurate seawater solution would still be better than RODI?

 

[BeanAnimal]

I am not so sure that VeeGee is not just the same rebranded stuff as everything else, honestly.


Also - I would calibrate with a known good reference at 35 ppt.