Most accurate method of measuring salinity?

[sleeri]

What is the most accurate method to measure salinity? Thinking about purchasing a digital salinity monitor, but wondering if they are accurate.

 

[Munch]

Just went thru this exact issue.

https://www.reef2reef.com/forums/reef-chemistry-forum/77538-salinity-3.html#post1197552

If you get a Hanna, you need to test it, and know it's baseline.

 

[sleeri]

Thanks!

 

[shellynjason]

The digital refractometers are suppose to be good.
I just bought a Milwakwee refractometer and can't get it to calibrate - keep getting an error so I think it's defective, it is based on a lenses reading. I have been using the swing arm but would love to double check it against a better refractormeter.

 

[medicme1]

I have a digital too although its ease of use is great. I do questions if its accurate too. so i show 1.026 but the lfs when they test it show 1.023 ugh

 

[shellynjason]

I bought a refractometer last night and checked my tank after calibrating, it showed 1.028 - Yikes!!! the swing arm has been showing 1.024 and the thermometer with sg always shows good at 1.024. Now I'm panicking to lower my salinity , assuming the refractometer is right and the other two are wrong.

Hope some more people chime in on this thread with their best salinity checker tool - this is a really good question.

 

[Bigdaddy]

my refractometer says .026 but my hydrometer says .028 no clue what one is right i also heard refractometer cal fluid goes bad after a while

 

[JLight]

Refractometers are usually much more accurate then hydrometers. I've never used a digital refractometer. But you gotta use ro/di water and calibrate the refractometer.

 

[dwilliams87]

You really shouldn't be using to/do to calibrate a refractometer. You should be using a solution that calibrates to the area you are checking. BRS has a solution that matches to 35ppt. If you calibrate to 1.000 and you are looking for 1.025, chances are good that your actual reading is around 1.027. You always want to calibrate testing equipment to the range in which you are testing.

Sent from my SGH-I777 using Reef2Reef Aquarium Forum mobile app

 

[fragmatic]

The swing arm plastic junks are notorious for being incorrect. You have so many things that can go wrong with them. IE: deposits, friction, amount of air in the water, salt in the pivot bearing, temperature, saturation, and others.

 

[Ron Reefman]

The swing arm plastic junks are notorious for being incorrect. You have so many things that can go wrong with them. IE: deposits, friction, amount of air in the water, salt in the pivot bearing, temperature, saturation, and others.

I suppose if you treat the swing arm hydrometer like crap, you will have problems like that. Just because they are cheap, you shouldn't treat them like 'junk'. I have a PinPoint meter, a refractometer and 2 swingarm hydrometers. I calibrate the PinPoint and refractometer with a calibration solution and then compare the hydrometers to them. They are both off by a small margin. So I label them both with the error rate.

Two years later I've recalibrated the PinPoint and refractometer 4 times (once a quarter). They have always stayed fairly accurate. The hydrometers, however, have been absolutely spot on every time (the same error rate that I labeled them with 2 years ago). So you can say what you want about hydrometers, but my experience is, once you know the built-in error rate (i.e. you calibrate it) it's every bit as accurate as a refractometer or digital meter. And it's MORE RELIABLE since it doesn't seem to need to be recalibrated.

 

[ReefPiracy]

All tools can come out of calibration. That is why I check my levels with friends everyone so often. Ive had tools i could never calibrate and others who it was dead nuts on for years. Depends on what you like. I when with digital but im a electronic guy. Old skoolers think im crazy . I found with the milwaukee it needs quite a bit of fluid to be right on. Calibrated fluid is the best way to check.

 

[mcarroll]

What is the most accurate method to measure salinity? Thinking about purchasing a digital salinity monitor, but wondering if they are accurate.

Lots of great replies so far!

I would only add that the question is a little too open IMO. I would ask "Most accurate for what?" since we know we're not really looking for the "most accurate in the world". :-D Is accuracy all you're really looking for in that digital meter? And further, is that all you get? As others have pointed out, a well calibrated swing-arm hydrometer can be a great solultion - even calibrated to your LFS's banged-up refractometer that's calibrated to RODI water will be good enough to manage your tank by.

I personally swear by the standard refractometer myself, but not as much for accuracy (which is great, and I calibrate by RODI) but for simplicity and speed as well as reliability in testing. I can pull identical tests from the same batch quickly and repeatedly, or quickly test many different samples. Not usually so easy or quick to get repeatable results with a hydrometer. IME, if you treat the refractometer as the fine tool that it is, you will not have problems with it coming out of calibration. I rinse mine in tapwater and dry it with a towel before storing it in it's foam case after each use. I check it regularly and it has never come out of calibration. If a refractometer is treated roughly, I'm sure your experience will likely differ. ;-)

I don't know how the digital meters will perform compared to these "analog" ones in terms of accuracy or other matters. Just looking at the Hanna HI96822's stats for an example, it reads out to the same number of decimals we're all familiar with, and to a +/- 0.002 accuracy.

There are obviously more factors than stats when selecting a tool, but I think by the stats an analog refractometer will give you results of at least comparable accuracy.

-Matt

 

[Bueller]

I started my tank on a hydrometer which said it was 1.024. I just received my refractometer and it says 1.039! It says use distilled water to calibrate it but ill try RO/DI. To calibrate do you just do it like you where testing it except leave it for about 30 seconds? I think it's best to compare for accuracy

 

[fragmatic]

Well, I got a surprise this AM. I decided to check the calibration of my refractometer. I found it to be calibrated at 38 and not at the 35 as my calibration fluid says.
I was having some problems; some zoa, a clam, a flower pot coral, and some candies were not growing. So, this means my salinity was at about 1.023.
Also, a brain stays alive but has never really had any serious extension.

Now, did my refractometer go out of calibration or did I have it calibrated wrong day one. I can not know, but I have never had much luck with zoa which leads me to think I never had it right. I think I screwed up.

Opinions or similar stories? Stories of a refractometer going out of calibration??

 

[Ron Reefman]

There is a reason why refractometers can be recalibrated and the people who make them sell calibration fluid as well... it's because refractometers can go out of calibration! I think most reefers will tell you to do it every 3 to 6 months. I did mine every 3 months for a couple years, now I use my hydrometer 90% of the time and only recalibrate the refractometer once every 6 months and then test my hydrometer against it. The refractometer usually needs a bit of adjustment, the hydrometer is always exactly the same error rate I found the first time I tested it and labeled it on the hydrometer.

I don'tknow for sure, but I have serious doubts that a salinity of 1.023 would cause problems growing zoas, a clam or candies, anything can cause problems with the flowerpot. Most animals we keep are fairly tolerent of small changes in salinity and temperature. I'd keep looking for other factors.

 

[bamareef]

All measuring instruments need a calibration check. Order fresh calibration solutions from vender where you purchased the tool. Rule of thumb, if you calibrate it monthly and you go about a year and no adjustments then you can space out the intervals to calibrate it to every couple months. I recomend checking at the minimum of 6 months. Also, test solution needs to be same temperature as what you measure your tank water. Also, be sure to clean tool with ro/di water after each use. I use a refractometer at work and never had any problems with it. At home i just use the float style, once i get done buying equipment i may get one for home.

 

[bamareef]

Also ask to see if the test solution comes with cal certifications when ordering solutions for calibration. You dont need them for home use, but will be your piece of mind you are getting good test solutions.