Refractometer help

[Tyler_Fishman]

I bought 2 refractometers on amazon, they are ATC, my question is concerning the specific gravity, mine often reads on both from 1.024-1.027 I would like a gravity of 1.026,and sometimes they do land on it, why do they do this? I follow normal refractometer usage protocol: wipe, calibrate, rinse, test, wash, although I notice when I'm done measuring salt and rinse it off and re calibrate it, reads 30 or 38 instead of 35, and so I have to adjust it again and again after almost every test. I'm stumped

 

[malacoda]

How are you calibrating them? If you're using RO/DI to 'zero' it, it's really not the most accurate method (. Better to get, or make, a 35 ppm saltwater standard and use that to calibrate.

These articles may be of help in shedding more light on the neverending 'refractometer calibration' discussion:

https://www.reef2reef.com/threads/calibrating-a-refractometer.283740/

https://www.reef2reef.com/threads/does-your-calibration-solution-need-calibrated.250133/

http://reefkeeping.com/issues/2006-12/rhf/index.php#11

 

[Tyler_Fishman]

How are you calibrating them? If you're using RO/DI to 'zero' it, it's really not the most accurate method (. Better to get, or make, a 35 ppm saltwater standard and use that to calibrate.

These articles may be of help in shedding more light on the neverending 'refractometer calibration' discussion:

https://www.reef2reef.com/threads/calibrating-a-refractometer.283740/

https://www.reef2reef.com/threads/does-your-calibration-solution-need-calibrated.250133/

http://reefkeeping.com/issues/2006-12/rhf/index.php#11

I use the solution

 

[saltyhog]

Make sure the cover is on squarely. If it's not it can affect the reading. Make sure there is enough water on the window to cover it uniformly when you close the cover. It should read exactly the same every time if you use the same sample.

I may be misunderstanding, but it sounds like you're saying if you recheck it after testing it no longer reads 35ppt?

 

[malacoda]

Hmmm, and you let the refractometers sit for 30-60 seconds after placing fluid on the lense so the temp can equalize? If so, then I'm stumped. Only other thing I can think of doing is taking it, along with a small sample of your tank water to a local tank store. While their ask them to measure with their equipment and also measure with your refractometers. If the readings don't match, maybe they can provide some insight as to what's going on.

 

[Tyler_Fishman]

Make sure the cover is on squarely. If it's not it can affect the reading. Make sure there is enough water on the window to cover it uniformly when you close the cover. It should read exactly the same every time if you use the same sample.

I may be misunderstanding, but it sounds like you're saying if you recheck it after testing it no longer reads 35ppt?

I made sure all those factors are in check, no bubbles on the prism, and I make sure it's uniform everytime, yes sometimes it does not read 35 ppt after re-administering the calibration fluid

 

[Tyler_Fishman]

I made sure all those factors are in check, no bubbles on the prism, and I make sure it's uniform everytime, yes sometimes it does not read 35 ppt after re-administering the calibration fluid

Yes I wait approximentally 45 second to a minute before usage, but sometimes when I'm a little impatient I'll use it at around 30 seconds. the odd thing is when that happens my readings tend to be lower, maybe that's the cause? How do you go about using your refractometer?

 

[Tyler_Fishman]

At the very least it does not yo far from a reading of 1.024 and 1.027, they usually read around 1.026 so I'm betting that is the salinity

 

[Idoc]

I'm not that particular, I guess. I calibrate it to 35ppt using the calibration fluid from BRS. I then put on a few drips of water, close the lid, and stick my eye up to the hole, fiddle with the focus whether it needs it or not (just habit) and take my reading. If i angle it down a little, i get a sharper line that's easier to read! Then wipe it off and forget about it until next time!

 

[saltyhog]

Sounds like your refractometer is defective. It shouldn't change in a matter of a few minutes.

 

[Tyler_Fishman]

After tinkering with it, it seems to have a stable reading of 1.025-1.026, both ranges I'm happy with, everything in the tank is fine, snails typically are the canary in the mine when it comes to water quality issues, so I guess it's ok