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

sjm817 · #1 10/18/2006, 07:53 PM

I got some Pinpoint 53mS salinity calibration fluid and tested my blue RHS 10-ATC (the cheap one everyone has) refractometer. It measured 1.030!!

The Pinpoint conversion chart shows it should read 1.0259, which is what I expect a calibration fluid would be set for. Now, if I check with plain RO, it does not measure 0, but is way below the scale.

I assume I should believe this calibration fluid?

cwegescheide · #2 10/18/2006, 08:02 PM

Randy has a recipie to make your own calibration fluid of 1.026 from a 2litre bottle and table salt. Worked perfect for me and verified it was accurate too.

Billybeau1 · #3 10/18/2006, 08:24 PM

Quote:

Originally posted by cwegescheide
Randy has a recipie to make your own calibration fluid of 1.026 from a 2litre bottle and table salt. Worked perfect for me and verified it was accurate too.

You must not have the cheapo.

Yes sjm, we have determined that the inexpensive refracts do not calibrate very well with RO or distilled.

My cheapo (properly calibrated) reads distilled water somewhere between - .0025 and -.0030

Here we go again

cwegescheide · #4 10/18/2006, 08:34 PM

Well brother pony up and get a NON-cheapo salinity meter!!! Get a nice refractometer and be done with it!!

sjm817 · #5 10/18/2006, 08:37 PM

I tried the DIY calibration fluid, but seemed to get a different result each time a made a batch. I guess my measuring cup skills are not that good. I never got the same amount of salt in the mix each time.

This is why I got the Pinpoint calibration fluid. Takes the me not making the calibration fluid error out of the equation.

So again, I can assume the Pinpoint fluid is accurate and now my refractometer is accurate?

Billybeau1 · #6 10/18/2006, 08:38 PM

Well brother, mine works just fine now that I know its properly calibrated.

sjm817 · #7 10/18/2006, 08:39 PM

Quote:

Originally posted by cwegescheide
Well brother pony up and get a NON-cheapo salinity meter!!! Get a nice refractometer and be done with it!!

I can live with the one I have as long as it is properly calibrated, which I believe it now is.

Billybeau1 · #8 10/18/2006, 08:42 PM

Quote:

Originally posted by sjm817
Takes the me not making the calibration fluid error out of the equation.

So again, I can assume the Pinpoint fluid is accurate and now my refractometer is accurate?

Yes sjm, I've had trouble making the DIY solution too. I've spent so much time on this subject, my head still spins.

I'll get Boomer to explain it again. (I think)

sjm817 · #9 10/18/2006, 08:54 PM

I think $3.45 for a bottle of calibration fluid is money well spent, especially for the "measuring cup impaired" people like us.

Billybeau1 · #10 10/18/2006, 08:58 PM

Yes I agree. I just want to make sure your calculations are correct since this has been such an issue. Boomer will be along in a bit.

sjm817 · #11 10/18/2006, 09:05 PM

I just went from what the Pinpoint conversion chart shows. It shows the 53 mS solution = 1.0259

PINPOINT™ Salinity Monitor
Conversion Chart

mS | ppt | SG
51.0 33.50 1.0248
51.5 33.90 1.0250
52.0 34.30 1.0253
52.5 34.60 1.0256
53.0 35.00 1.0259
53.5 35.40 1.0262
54.0 35.70 1.0265
54.5 36.10 1.0268
55.0 36.50 1.0270
55.5 36.80 1.0273
56.0 37.20 1.0276
56.5 37.60 1.0279
57.0 38.00 1.0282
57.5 38.30 1.0285
58.0 38.70 1.0288
58.5 39.10 1.0291
59.0 39.50 1.0294
59.5 39.80 1.0296
60.0 40.20 1.0300

Billybeau1 · #12 10/18/2006, 09:13 PM

It doesnt surprise me that once you calibrated with the 53ms solution that your refract registers lower than 1.00 with ro or distilled. Thats my whole point.

My whole point (months ago) was that even though the manufacturer of the inexpensive ones says you can calibrate with RO or distilled, this is just not true.

I'm just not good as explaining the reasoning as Boomer.

My head still hurts.

bertoni · #13 10/19/2006, 12:55 AM

The calibration solution for a conductivity meter likely won't work at all for a refractometer. The conductivity of a solution and its refractive index are not necessarily correlated if the ionic balance isn't fixed. So the conductivity solution is set up to have a certain "resistance", and its components might not at all resemble seawater, so its refractivity could vary greatly from seawater with that same "resistance".

Bottom line: you can't use a calibration standard for both a conductivity meter and a refractometer unless it was carefully designed to work with both.

sjm817 · #14 10/19/2006, 05:32 AM

Thanks for the reply. That makes sense. I'm going to send American Marine (Pinpoint) an email and see what they say too.

sjm817 · #15 10/19/2006, 06:22 AM

Wow, I emailed AMI @ 6:30 this morning and got a reply @ 7:00! He said the calibration fluid should read 1.026 on a refractometer.

Randy Holmes-Farley · #16 10/19/2006, 07:14 AM

Hold on everyone!

The 53 mS standard provided by pinpoint may ONLY acceptable for conductivity meters. It is not likely to be 53 mS/cm seawater, but rather another chemical, and so will not necessarily match the refractive index of 53 mS/cm seawater and cannot necessarily be used to calibrate a refractometer.

That said, Lou Dell may have designed it to be suitable for a refractometer as well, but I am skeptical of that, and I'll invite him here to confirm this.

sjm817 · #17 10/19/2006, 07:31 AM

The email I got was from Lou Dell:

Quote:

It should read 1.026 on your refractometer. If you send me the bottle I
will verify it and send it back...Lou Dell/AMI

Randy Holmes-Farley · #18 10/19/2006, 09:24 AM

I know you said that, Lou emailed me this morning the same, but I am still skeptical and will continue to follow up with him.

sjm817 · #19 10/19/2006, 09:59 AM

Thanks Randy. As usual, your help is greatly appreciated. I swear, I dont know how I would be able to keep my system going without help from experts such as yourself.

Boomer · #20 10/19/2006, 10:58 AM

I'm going to have to see proof that a PinPoint 53 mS works on a refract. No, it is not impossible but I wonder if Lou is just confused. However, it would be great if it did work on a refract and EC meter or even a SG hydrometer. There are solutions that will work on all three but are very, very pricey.

I might add Lou's table is off also

53.0 35.00 1.0259

That table to be std, which it should be, should be

53.0 35.00 1.0264 and not 1.0259

That would have to be a table for a hydrometer calibtated @ 77F and being used in 80F water. And he shows no ref for temp for SG

sjm817 · #21 10/19/2006, 11:47 AM

Randy, Boomer, Billy. If you would like, I can send some of the fluid to you and you can check it against your refractometer and analyze it. PM me if interested.

Randy Holmes-Farley · #22 10/19/2006, 11:49 AM

Well, I think we can work it out with Lou. He and I discuss things about his products reasonably frequently (and besides, I don't have a refractometer

).

sjm817 · #23 10/19/2006, 11:52 AM

Quote:

Originally posted by Randy Holmes-Farley
Well, I think we can work it out with Lou. He and I discuss things about his products reasonably frequently (and besides, I don't have a refractometer ).

I guess you are still using a Hydrometer

I'm glad you guys interviened before I started raising the SG of my tanks. I'll hold off until things are confirmed.

Boomer · #24 10/19/2006, 12:08 PM

We use very expensive EC meters, aka, Conductivity/Salinity meters

These are the std for seawater.

Randy Holmes-Farley · #25 10/19/2006, 12:18 PM

I guess you are still using a Hydrometer

No, I like conductivity.

FWIW, the Pinpoint conductivity probe is a good way to go, although I use a more sophisticated lab meter.