need your thoughts on Refractometer calibration

[Black71gp]

ok need your opinion.

I have 35 ppt calibration fluid i use for my refractometer. works great for the reef. However I am treating my fish with hypo salinity. If i check my meter with RO water it is a little ways below 0. so my thought was to calibrate it for the RO water since it is closer to the 1.008 i am shooting to get my salt to for my fish, rather than 1.026 (35)ppt that my calibration solution is for. What are your thoughts. My reads about a .003 difference between the two calibration points. so should I leave it calibrated with the solution at 35 ppt or calibrate it with RO water at 0 to get the most accurate measure at 1.008

Thanks

Jarrod

[schminksbro]

Use the fluid and then mix the salt to the level that you want it. The refractometer will still be calibrated and accurate.

[MizTanks]

Not hitchhiking but this is good for a question I have. I have no fluid to calibrate refractormeter , lfs doesn't sell it. Is there any other way to do it? I'm back to using my hydrometer :/


There is nothing like being a REEFER!

[handlevandal]

Marine Depot

http://tinyurl.com/2a3yjyj

[BeakerBob]

Most of the refractometers sold for this hobby are not linear in their measurement from 1.000 to 1.040. Because of that, they should be calibrated at or near their point of use.

If you want an accurate and consistent (precise) measurement at 1.008, I would calibrate with RO water.

Alternatively, you could purchase a laboratory grade refractometer that is linear from 1.000 to 1.040 or get a calibration fluid that measures 1.010 and use the current refractometer.

You can always dilute the current calibration fluid in half to get a 1.013 fluid.

[rmalone]

I would use distilled as a cal solution, I agree that you should calibrate at or near the target value.

[MizTanks]

Ummmm still don't understand sorry. What is meant by " calibrate it to 1.040b


There is nothing like being a REEFER!

[fishtal]

Most of the refractometers sold for this hobby are not linear in their measurement from 1.000 to 1.040. Because of that, they should be calibrated at or near their point of use.

If you want an accurate and consistent (precise) measurement at 1.008, I would calibrate with RO water.

Alternatively, you could purchase a laboratory grade refractometer that is linear from 1.000 to 1.040 or get a calibration fluid that measures 1.010 and use the current refractometer.

You can always dilute the current calibration fluid in half to get a 1.013 fluid.

Bob,

How does this one measure up in your opinion?: http://www.aquacave.com/milwaukee-salinity-refractometer-brwith-atc-by-milwaukee-brinstruments-mr100atc-616.html#

[BeakerBob]

Bob,

How does this one measure up in your opinion?: http://www.aquacave.com/milwaukee-salinity-refractometer-brwith-atc-by-milwaukee-brinstruments-mr100atc-616.html#

Much better in quality!! This one should perform like you want.

[BeakerBob]

Ummmm still don't understand sorry. What is meant by " calibrate it to 1.040b


There is nothing like being a REEFER!

Jamie, where does it say to "calibrate it to 1.040b"?

[Black71gp]

I like the idea of 50/50 mix I think i will aim for that for calibration for the treatment

[MizTanks]

Alternatively, you could purchase a laboratory grade refractometer that is linear from 1.000 to 1.040 or get a calibration fluid that measures 1.010 and use the current refractometer.

See right up there^^^ :)


There is nothing like being a REEFER!

[BeakerBob]

Ummmm still don't understand sorry. What is meant by " calibrate it to 1.040b



Alternatively, you could purchase a laboratory grade refractometer that is linear from 1.000 to 1.040 or get a calibration fluid that measures 1.010 and use the current refractometer.

See right up there^^^ :)

Most of the inexpensive refractometers are not linear from 1.000 to 1.040 (or higher). This means that they are not accurate in the whole range of measurement. That's why you cannot calibrate it with RO water (1.000) and expect it to measure accurately to 1.026, the normal reading of SW. You need to calibrate these types of instruments at or near it's point of use.

A good laboratory grade refractometer is linear from 1.000 to 1.040 (or higher), so that you can calibrate with water at 1.000 and it is still accurate to 1.040. Conversely, you could calibrate at any point and it would be accurate throughout its measuring range.

[fishtal]

Much better in quality!! This one should perform like you want.

Good to know. That's the one I have. :)

[jenghes]

Here is a great article on refractometer calibration and it gives directions on how to make calibration fluid.

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