My refractometer is way off when testing with Pinpoint 53mS calibration fluid

[lilprincess]

FWIW, I have the blue handled RHS-10ATC refractometer, set it to 0 with ro/di and tested with the 53ms solution. My reading came out +.002

[Boomer]

Billy

Randy and I think it is due to varying optical qaulity in cheap meters. We do not know what kind. He will talk about this somewhat in his article

[Cosmo^Kramer]

I just received a ASICO SALINITY REFRACTOMETER from Premium Aquatics for $39.95.I calibrated with RO/DI and then the CAL FLUID 53.0MS,it's right on the money with both,0 ppt with RO and 35ppt with the Calibration fluid.It is the black handle with the calibration screw on the top.In steo 3 on PA's website it states that if you calibrate with the cal. fluid then RO the RO will read negitave,but mine is right on.The one I have is the top pic sjm817 posted on page 8

[Randy Holmes-Farley]

I think the answer may just be that if you make something with low enough quality controls, it may not be accurate enough in all cases, but in some it will be.

[Aquaduck]

Originally posted by Randy Holmes-Farley
I think the answer may just be that if you make something with low enough quality controls, it may not be accurate enough in all cases, but in some it will be.

Kind of like the old saying that if you get an infinite number of monkeys and put them infront of a infinite number of typewriters for an infinite amount of time, at some point one of them will write the works of Shakespeare.

At some point all the "good" parts come together to make an accurate recractometer.

[jeffbrig]

Remember, even a blind squirrel finds a nut every once in a while.

[Konadog]

OK, I have read thru this thread and have a question, is there a reason that when making the calibration solution, that we make so much? Is it due to the ease of measurement, or something else? Is there a way to just make a cup of the stuff?

[bertoni]

If you have a sufficiently accurate scale and other measuring equipment, you can make it in smaller quantities. I'm a wimp and use the PinPoint solution (for my conductivity meter).

[Konadog]

That would be the easy way. I use a measuring cup to hold what I think is enough (more or less)

Just wondering if there was a "scientific reason" to make two liters of the stuff.

[jeffbrig]

Since you're dealing with approximate volumes and measures, the larger volume = smaller % errors. To mix smaller quantities, your measures would need to be much more precise.

[Konadog]

Now that I understand! Thanks

[Doni]

I also have the blue handled RHS-10ATC refractometer; it tested zero using ro/di and 35ppt using Pinpoints calibration fluid.

[SA057]

Originally posted by Doni
I also have the blue handled RHS-10ATC refractometer; it tested zero using ro/di and 35ppt using Pinpoints calibration fluid.

Same for me.

[Billybeau1]

I must have bad ro/di.

[Boomer]

DP

[Boomer]

Billy

No such thing for cal'ing a refract. Remember that a 1 on that refract = 1,000 ppm or a 1.0% solution. It is a quality control optics thing That is easy to mess up Lots of people have had - values and some even + values. Your meter is just telling you that it will be more off at lower salinities. An expensive lab grade refract should be off - 1.5 points. As of yet no one has had one to test. I'm still waiting to hear for Atago a world leader in refracts. Their's is $275.00

[Doni]

Hummm... so mine is accurate on and around 35ppt but inaccurate for hyposalinity. I can work around that for now... if needed, I will purchase the PinPoint salinity monitor.

[tfp]

looks like my rhs-10atc is a winner
tested spot on 35ppt with the pinpoint salinity calibration fluid.

[Randy Holmes-Farley]

FWIW, my detailed article on refractometers, including calibration issues, will post on about Dec 5 at www.Reefkeeping.com

[tylorarm]

Ok, i just tested my RHS-10ATC blue handled gem with your solution at 1.030 or 40. Not good. Once calibrated with this solution my tank reads 1.020 instead of 1.025. I also tested with my old swing arm and tank reads 1.023. I probably errored a bit with my crude measuring devices, but one way or another I need to bring my SG up. Such a low SG could also help explain why my TM Pro Salt has dKH of 7.2 and Mg of 1100 area. I plan to add NSW to sump and let evorporate until osmolator kicks in. If I have 150gl of total water how much NSW do I need to add to raise SG by 0.001 (to 1.021 new calibration or 1.026 old calibration)?

[Randy Holmes-Farley]

If I have 150gl of total water how much NSW do I need to add to raise SG by 0.001 (to 1.021 new calibration or 1.026 old calibration)?

About 4% of the tank volume.

[kelley_mc]

Originally posted by Randy Holmes-Farley
FWIW, my detailed article on refractometers, including calibration issues, will post on about Dec 5 at www.Reefkeeping.com

I look forward to reading! Thanks for all of your efforts on this.

[Randy Holmes-Farley]

Happy reefing.

[Mental1]

Okay -- after much ado about everything, and to add one more piece of conflicting and corroborating data to the mix -- I have a blue handled RHS-10 ATC calibrated with Randy's homemade recipe mixed using a RCBS 5.0.5 scale by Ohaus Corp converting grains to grams and a syringe for the ml -- after calibrating to 35 ppt my RO/DI water measures in at -.03+. Both tanks are off.
Amen to Happy Reefing!

[Randy Holmes-Farley]

Glad it was helpful for you.