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

[cham]

Agreed.

And while SG is only ONE factor IMHO its very importiant one. And really what were talking about here is a $3.00 bottle of solution that makes a difference of a innacurae cheapo and an accurate cheapo.

Three bucks.

[cwegescheide]

Originally posted by Randy Holmes-Farley
Actually when I saw a big discrepancy between what my refracto I took my refracto to the Florida Aquarium to have the pro's verify my reading. I know that sounds a little extreme but I can walk there from my place. I was surprised that they were VERY helpful and cool people. Once they dialed it in and I came back I then tried the Randy's Homemade calibration fluid again. It measured 1.026

That's good to hear. Did you make it by cup sand coke bottles, or by weight?

Do you know what they did to the refractometer?

I think they just initially calibrated it to zero with tap water actually. I wasnt allowed into where they did it but thats what they said they did. Then they checked my reading in one of their tanks to the refractometer they used.

I used the 2litre coke bottle and (I can't remember exactly) i think it calls for a cup of table salt. I poured the contents of the 2litre totallly filled into a big bowl i had and then added the required amount of salt. Mixed it up real good and let it sit for a little. 1.026 on the dot.

Chris

[barjam]

After reading this thread I must say that I'm a little suprised with what some of you have said.

In my case the concern was hyposalinity. I really don't care if my main tank is 1.024 or 1.026 as long as it is stable.

[gophia]

Randy er al., wouldn't it be easier to make a standard using our synethic salt such as IO instead of using table salt?

[Randy Holmes-Farley]

No, using salt mix is not suitable because it has variable and unknown (to me) amounts of moisture in it.

[Boomer]

IMHO there are to many variables of where the mix is changed every so often. Bag to bag is also some times different. Then there is the issue who's salt should be used. It is much more exact to use Randy's DIY or PinPoint's 53mS.

Bar

If hypo is the issue then just get a Aquarium Systems swing arm or a Tropic Marine bulb type hydrometer.

[cham]

Or for hypo you can recalibrate using RO/DI. Once done with hypo recalibrate using 53ms solution.

[Boomer]

Sneaking in some of the diagrams early Randy . Look nice .

[IndyReefMan]

I mixed up some of Randy's calibration solution and measured it on my black handled refractometer from MD and it showed 43PPT. I couldn't believe that my refractometer was that far off.. I hadn't seen anyone else report that large of a discrepancy so I mixed a second batch to double check and it came out the same. I set my refractometer to 35PPT using the solution. Then, I checked the SG on my tank. It showed 1.018. All this time I thought I was keeping it at 1.025. Premium Aquatics is out of their calibration solution (big surprize, huh) so I'm reluctant to start raising the salinity until I can order some and check it. I don't have any means of accurately weighing the salt and water for Randy's calibration solution so I had to use a measuring cup and Coke 2L bottle. I don't know how accurate I was since there is a warning on Randy's recipe about variances in those coke bottles. I guess I'll just have to wait.

[Randy Holmes-Farley]

IndyReefMan:

That is very far off. Can you describe exactly what you mixed up? We might be able to troubleshoot the mixing to be sure there is no apparent issue.

[Krugar]

Quick question:

On the RHS-10ATC model, the instructions specifically state that when calibrating the ambient room temperature is to be 20C (68F).

If I instead calibrated at 22C (71.6F), using RO/DI water would this have any impact when testing around 35ppt sea water?

Or is this just a bunch of crap from the manufacturer?

Cheers!

[Randy Holmes-Farley]

We've discussed that before and could never understand that claim for an ATC refractometer. In any case, 2 deg C is not going to be an issue.

[IndyReefMan]

Originally posted by Randy Holmes-Farley
IndyReefMan:

That is very far off. Can you describe exactly what you mixed up? We might be able to troubleshoot the mixing to be sure there is no apparent issue.

My bad... I accidentally used the wrong measuring cup. I measured 1/3 cup Mortons salt instead of 1/4 cup Mortons salt (that's why my wife does the cooking instead of me... LOL). I mixed up a new batch. It now appears that my refractometer has been reading approx 0.003sg too low. I calibrated it to 35PPT on the new batch and then subsequently measured it using RO/DI water. It is about 0.003sg below the zero line. I've ordered a Pinpoint Salinity Monitor from PA. I've been looking for an excuse to get one anyway. My eyeballs are getting too old to be trying to read those tiny little refractometer lines anyway.

[catalyst]

if PA is still out of stock on the Pinpoint 53.0mS Calibration Fluid, you can get it from the manufacturer, American Marine:

http://www.americanmarineusa.com/

I ordered on Monday and rec'd it today

(2) 2oz bottles for $5

I calibrated against both ... guess I am one of the lucky ones - my 10RHS-ATC was set correctly

[boxfishpooalot]

Originally posted by Randy Holmes-Farley
That concern applies when calibrating at a point far from where you'll use it. If you calibrate at the exact point where you use it (35 ppt seawater), it will be fine.

So should I calibrate my refractometer based on your salt solution? Or use ro water?

[barjam]

Off topic and removed.

[SA057]

I calibrated against both ... guess I am one of the lucky ones - my 10RHS-ATC was set correctly

Yea, I used Randy's salt mix a few months ago and found mine was right on too. Mine zeros with RO and was at 35PPT with the mix.

[catalyst]

I was a bit concerned when I found this thread ...

it was a relief to find that my tanks *have* been at the correct salinity for the past 2 years

[The_Taz_Devil]

When I had a FOWLR system I had a deltec refractometer which was calibrated with plain RO water and I always thought it was accurate. A little while ago I invested in a pinpoint salinity monitor and found that there was a difference of 0.004 between the 2 (i.e the refractometer measured the salinity at 1.026 and the pinpoint monitor at the equivalent of 1.022). Not so bad in a FO system but so glad I did. I thought I just had a faulty refractometer.......maybe should have brought this up at the time (nearly 12months ago).........

[jeffbrig]

I happened to check my tank's salinity this morning, BEFORE I found this article. I was at 1.023, from skimming wet and not checking salinity regularly. Not good, but easily corrected, right?

My refractometer (RHS-10ATC) is calibrated to 0 with 0tds RO/DI water. This evening, I mixed up Randy's 35ppt DIY calibration solution, and it read 38-39ppt (1.029) . I dialed it back to 35ppt and rechecked the tank: 1.020 / 27ppt

I'm absolutely reeling at this point. I have the double whammy of thinking I was low to begin with, and THEN finding out that my refractometer was reading high, meaning I'm even LOWER!! At that level, it's a wonder any corals/inverts are doing well.

I don't trust this refractometer at all anymore, since it evidently has a BAD slope error. I need something that can be trusted in my tank, as well as for hypo in QT. I think I'm going to spring for the Pinpoint salinity monitor, any comments on this item?

http://www.marinedepot.com/md_viewIt...product=AM1115

Jeff

[catalyst]

not necessarily a bad slope mirror...

as Randy mentioned earlier in this thread - you cannot expect accurate results from a scale of 0-1 when you calibrate at 0 - you must calibrate to the value you will test, ie 1.024 or 35

just reset your refracto based on the calibration solution you made up and go forward

I chose to wait 2 days and get a second calibration sample from American Marine - and I'm glad I waited

[catalyst]

but if you *must* get a new refracto, bomber mentioned earlier in the thread that True Saltwater Refractos* run $100 or $200 or $500 - and that the filtersguys.com (?) have the $100 model available for sale

*our chinese 10RHS-ATC's are (table) salt (NaCl) refractos

[jeffbrig]

I understand what you are saying, but if I calibrate to 1.026, I will have an error when I measure for hyposalinity at 1.009. Clearly the slope is incorrect in this refractometer, as illustrated in Randy's diagrams above. Since I cannot calibrate the meter so that it is correct at both target values, it will be replaced with something that can (a salinity monitor). I have way too much money invested in this hobby to rely on an inaccurate piece of equipment, especially with something as fundamental as salinity.

If you think my refractometer is worth having, I'll give it to you for a song...

[catalyst]

you should save it and calibrate it to your target of 1.009 for your hypo tanks

I have 2 pH meters - one SW, one FW

[catalyst]

but now that you mention that, I guess I will need another refracto myself