Lesson learned about using R/O for refractometer calibration

[bobman]

Just make sure it is for seawater.

I have always used RODI and for our home aquarium you will be fine however if you find you seem to be always adjusting your to read 1.000 with rodi it would not be a bad idea to get some calibration fluid a then see if you read 1.0000 with rodi after you calibrated with the fluid if it does not repeat then I have to agree with russ you refratometer is toast and out of calibration. Also if reading you tank water say its 1.025 check it again in about an hour or 2 if its not 1.025 its toast. We have a calibration department here at work and although we dont use refractometers here we use many different tools one thing is even if they can calibrate it if they are constantly having to adjust it then that is a very good indication something is wrong and for the price of another one its just not worth the headache

 

[bubbaque]

Thanks for all the help! Just going to buy another one tonight.

 

[Russ265]

Thanks for all the help! Just going to buy another one tonight.

just research a bit. you have a lot of great info here.

im not saying buy red sea. there are a ton of good ones that arent name brand.

 

[reeferfoxx]

I used the red sea eye piece-o-c... Or at least thats what I dubbed mine. Mine seemed to work for maybe a month or at least i thought it did. What would happen is, i calibrate it, test water, water is off by 1 ppm. So i test refractometer with 35ppt solution, comes up 35ppt. So I test water again, its now +2ppm. So I recalibrate refractometer. Then back to testing tank water. Water is now right where it should be, 1.025....

2 weeks later, the hinge is rusted and the dismal task of recalibrating commences.

Get a Milwaukee and call it done.

 

[blacktippr]

I used the red sea eye piece-o-c... Or at least thats what I dubbed mine. Mine seemed to work for maybe a month or at least i thought it did. What would happen is, i calibrate it, test water, water is off by 1 ppm. So i test refractometer with 35ppt solution, comes up 35ppt. So I test water again, its now +2ppm. So I recalibrate refractometer. Then back to testing tank water. Water is now right where it should be, 1.025....

2 weeks later, the hinge is rusted and the dismal task of recalibrating commences.

Get a Milwaukee and call it done.

X2 on the Milwaukee digital refractometer. Best 100 dollars I've ever spent.

 

[jason2459]

I highly recommend the vitalsine that can be found at doctor foster and smith or the veegee at the filter guys. They are the same refractometer. Very well made, holds calibration extremely well, and an easy to read clear full scale. Plus its a true seawater refractometer. I trust it more then any others I've used.

Second recommendation for a refractometer would be the Milwaukee seawater digital refractometer. Very easy to read and easy to calibrate to 0 with distilled or ro/di water. Then can be cross checked with a calibration solutuon. Only downside is that its not as high of resolution as the veegee but really not that big a deal.

 

[Ontheway]

I am using Rodi water. This is how I do it, first I adjust calibration room temp close to water temp to be sure there is no high difference. Then I let refractometer sit in the room for 15-20 min. with headpart touching to nothing (ie sitting on side of table). Same waiting period for rodi calibration fluid. Then calibrate it to 1.000; this is done in two steps, drop the fluid and measure after 15 secs., adjust it to 1.000. Then let device sit on table with headpart metal is on air, 3 min later, check again. If both same, Its done. I use same 2times system for measurements, too.
Although I switched to Milwaukee digital sometime ago, for easy operation.

 

[tjnorthdakota]

you guys are making this to complicated, all you have to do is get 1 liter fresh made saltwater boil it down in a beaker and bunson burner and measure the remains on a lab cerified and recently calibrated scale done at sea level. you'll have your mg/L, convert and compare to your refractometer.

 

[Downbeach]

http://reefkeeping.com/issues/2007-03/rhf/index.php#14

 

[Sharvey103]

I use both RO to zero out then a purchased cal solution and one a make. There are variations in different batch of calibration solutions from the same vendor.

 

[MCooper]

This is a very interesting issue as I am not sure what is best method personally. I bought some salifert calibration fluid and used that.

 

[redfishbluefish]

First off, there is no need for the OP to purchase a new refractometer. The one you have is just fine.

You calibrate at 1.026 and then when you test, your most accurate reading will be when you're measuring saltwater at 1.026. I've never tested RO/DI water, and if I did, I'd calibrate using RO/DI water. There is no reason to put RO/DI water in your refractometer to test....or to calibrate. Use it to clean your refractometer and that's about it.

The linearity of your refractometer between SG 1.000 and 1.026 has nothing to do with how much you paid or were you purchased the unit. High priced refractometers from the biggest names still need to be calibrated with calibration fluid. I've used high priced and low priced refractometers, and currently have a low priced refractometer that works just fine. If you wish to measure RO/DI water after calibrating with 1.026, and find it's not 1.000....that's fine, because you're not using your refractometer to measure RO/DI water.


I'm trying to think of analogies about calibration......pH: Regardless of the cost or quality of a pH meter, I wouldn't want to use pH 4 and 7 calibration solutions if I'd be measuring something at pH8. If I did, and then recalibrated using pH 7 and 10, I'd most likely get a different answer. It has nothing....NOTHING....to do with the price, quality and brand name on the unit, but has to do with good scientific practice. Calibrate with solutions closest to what you will be measuring.

Here's one for the gun enthusiasts: I would not adjust for windage on my riffle in a 30 mile an hour wind and then, without making changes expect to hit the bull's eye using the same correction on a calm day. You calibrate to what you're current situation is. (I'm not sure if this one is a good analogy???, but I like it.)

 

[reeferfoxx]

I highly recommend the vitalsine that can be found at doctor foster and smith or the veegee at the filter guys. They are the same refractometer. Very well made, holds calibration extremely well, and an easy to read clear full scale. Plus its a true seawater refractometer. I trust it more then any others I've used.

Second recommendation for a refractometer would be the Milwaukee seawater digital refractometer. Very easy to read and easy to calibrate to 0 with distilled or ro/di water. Then can be cross checked with a calibration solutuon. Only downside is that its not as high of resolution as the veegee but really not that big a deal.

The problem i have with eye piece refractometers is the scope. The scope is like any other scope. You can look through it and clearly read the salinity but depending on what angle your eye is sitting can skew the results.

You are correct on the Milwaukee. It sort of rounds the number. However not that big of deal. But it calibrates very quickly and it reads samples very quickly. Both win wins for me as im always on the go.

 

[reeferfoxx]

The linearity of your refractometer between SG 1.000 and 1.026 has nothing to do with how much you paid or were you purchased the unit. High priced refractometers from the biggest names still need to be calibrated with calibration fluid. I've used high priced and low priced refractometers, and currently have a low priced refractometer that works just fine. If you wish to measure RO/DI water after calibrating with 1.026, and find it's not 1.000....that's fine, because you're not using your refractometer to measure RO/DI water.


I'm trying to think of analogies about calibration......pH: Regardless of the cost or quality of a pH meter, I wouldn't want to use pH 4 and 7 calibration solutions if I'd be measuring something at pH8. If I did, and then recalibrated using pH 7 and 10, I'd most likely get a different answer. It has nothing....NOTHING....to do with the price, quality and brand name on the unit, but has to do with good scientific practice. Calibrate with solutions closest to what you will be meas.

Why does the calibration solution have to be closest to the specific gravity you are going for? Would 0tds rodi or distilled water throw the reading off?

Another reason not to get an eye piece-o-c...

 

[jason2459]

Why does the calibration solution have to be closest to the specific gravity you are going for? Would 0tds rodi or distilled water throw the reading off?

Another reason not to get an eye piece-o-c...

You should try and calibrate as close to the end point you are trying to test for. Like with pH we use 7 and 10 solutions and not others like 4. If using a conductivity probe we should calibrate to 53mS and not 0. Milwaukee doesnt give any option though other then 0. But then I will still use the calibration solution to test for accuracy at 35ppt like in that thread I started on does your calibration solution need calibrated.

 

[Anirban]

Here is the next best step...
Have your water tested by the Triton ICP testing and compare it to the refractometer reading

Actually there is a comparison post across all these measurement processes including Triton by @Berlibee . Here is the link...

https://www.reef2reef.com/threads/i-run-my-system-at-1-029.230701/page-6#post-2733207

 

[jason2459]

Actually there is a comparison post across all these measurement processes including Triton by @Berlibee . Here is the link...

https://www.reef2reef.com/threads/i-run-my-system-at-1-029.230701/page-6#post-2733207

Yes, which refernces JimWelsh's spreadsheet for calculating the estimated salinity based on the Triton results.

He used my spreadsheet to calculate salinity, and inferred a SG from that. The results he posted here show a salinity of 36.61, which translates into a SG of 1.0276 at 25C.

 

[rckfsh44]

I was using R/O water to calibrate my refractometer. I wasn't having any issues with the tank but I thought it would be a good idea to buy some calibration fluid from BRS just to make sure it was fine. I thought my salinity was at 1.026, when in reality it was close to 1.022. I will never calibrate using R/O water again and if you are currently doing so, I would suggest buying some calibration fluid.

Thy are right I learned a long time ago about the calibration fluid , mine was a few years old , so I go into the LFS, and they say use RO Water I said no thanks

 

[Anirban]

Yes, which refernces JimWelsh's spreadsheet for calculating the estimated salinity based on the Triton results.

So in case somebody want to really know and satisfy himself about exact salinity measurement by their refractometer then go for triton and cross check...

 

[jason2459]

So in case somebody want to really know and satisfy himself about exact salinity measurement by their refractometer then go for titon and cross check...

It will be close but not exact. Also, calibration solution bought may also not be exact. You can make up your own but it also depends on you and your equipments accuracy so may not be exact. There's always a +/- varrience.

And sometimes its beyond that varience.
http://reef2reef.com/threads/does-your-calibration-solution-need-calibrated.250133/