Tips for less frequent calibrations of refractometer?

[salty joe]

As has been mentioned, making sure the refractometer is clean and about the same temp might help.

I get the same results with a warm white LED and daylight. As long as there is a sharp line on the scale, I don't see what difference the light source makes.

I've had a cheap refractometer for 10 years or so. It supposedly adjusts for temp. A difference between high dollar and inexpensive models is the ability to accurately measure water over a wide range. I calibrate mine at 35 ppm and that's all it's used for. I hadn't used it for a few years and it was a couple points off then checked it a month later and it was a point or so off. Since then, about 9 months, it's been steady. I like to check it every time. I like it a lot. Especially considering what it cost.

 

[malacoda]

Let's not forget about the calibration fluid either...

If it has been sitting for a while, shake up. I've had a bottle that was only a few months old that was reading ~4 ppt low. Gave it a good shake, took another reading an it was spot on. Can only assume it was a bit of settling or precipitation in the bottle.

And if it's really old it should be replaced. Over time evaporation will change it's salinity.

 

[mjpinsky]

calibrate refractomete

calibrate refractomete

I followed another post from years ago, and their trick worked.
Instead of buying expensive calibration fluid I use pure distilled water (that I also use for my CPAP machine). The reading should be dead-on at 0.00.
It is the cheapest and easiest calibration fluid. (A gallon will cost about 70 cents US).
When I bring in samples to my LFS, they always get the same reading as me, so it must be working.
P.s.: My refractometer only has required recalibration twice in past 5 years.

 

[hogfanreefer]

My original refractometer never varied for almost 4 years. However the pin that holds the plastic cover rusted making it difficult to use. My new refractometer is requiring recalibration every few days. It's never off more than 0.001 but it will get off by that much pretty quickly.

Chemistry professors always told me to calibrate the instrument in the range you would be testing.

 

[salty joe]

Chemistry professors always told me to calibrate the instrument in the range you would be testing.

I agree 100%

 

[outssider]

I followed another post from years ago, and their trick worked.
Instead of buying expensive calibration fluid I use pure distilled water (that I also use for my CPAP machine). The reading should be dead-on at 0.00.
It is the cheapest and easiest calibration fluid. (A gallon will cost about 70 cents US).
When I bring in samples to my LFS, they always get the same reading as me, so it must be working.
P.s.: My refractometer only has required recalibration twice in past 5 years.

if your LFS calibrates with distilled/rodi water at -0- they may be off the exact same amount as you. If you do a little research, you will learn that it's always best to calibrate at the range you will be using the refractometer at. It only requires 2 drops of calibration fluid so unless you're calibrating a 100 times a day I don't see where you would be saving much. I calibrate and test my water only at water change time (once a month). some refractometers will still be accurate at 35 ppt when calibrated at 0, most will not.

 

[der_wille_zur_macht]

People talk about hydrometers like they are junk and refractometers are the gold standard. I'll take a calibrated hydrometer any day!

Glad I'm not the only one who feels like this. I remember when I first started hearing about refractometers becoming popular maybe 10-15 years ago, and it seemed like instantly everyone assumed every single hydrometer on the planet was wrong, and every single refractometer was always right no matter what. I feel bad for all the newbs who came on forums and were told to discard their hydrometers for a "way more accurate" refractometer, with no explanation about calibration or understanding what a refractometer even was.

I got completely out of the reef hobby when I took down my 360g a handful of years ago, sold every single piece of reefkeeping equipment. When I started back up a few months ago, I bought another refractometer. It was off by about 30% out of the box. It has stayed put since I calibrated it that first time, but I shudder to think about some innocent newcomer using an instrument with that kind of error as the gold standard. I wish I'd kept at least one of my old hydrometers.

I guess the moral is, no matter what you use, make sure you understand your instrument and it's associated methods. And if anything feels out of whack, double check against a solid known standard.

 

[tmantaylor18]

Is it the Red Sea refractometer?

If so good luck with that thing. Im on my second one now under warranty and these things don't hold calibration at all. I took my first one back to my LFS and they couldn't get it to work either. I then found a bunch of reviews online saying the same thing about theirs. This was a good reminder to myself why I like to shop online or at least check for reviews before buying. Red Sea has denied sending me any other usable supplies in return for this broken refractometer.

End rant :headwally:

 

[Han Solo]

I calibrated mine with solution and then put a tiny bit of thin super glue to hold the calibration screw. It always seems to turn alittle. If it's off when I check it again I'm sure I can get it out.