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#1
07-12-2009, 04:44 PM
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all that confirms is that swing arms are not accurate between different brands.. there is a 0.006 differance in ranges on the same solution between the different brands.. to bad he didn't buy 6 og the same type and do it.. you would have seen the same type of readings. now having said that refractoemters can be wonkey also.. you have to buy a quality unit with temp compensation. you do get what you payfor in refractometers and personaly I would not buy one under 100 bucks. Steve
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 *everything said above is just my opinion, and may or may not reflect the views of this BBS, its Operators, and its Members. If cornered on any “opinion” I post I will totally deny having ever said this in a Court of Law…Unless I am the right one*Some strive to be perfect.... I just strive. 
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#2
07-12-2009, 04:59 PM
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"It is my opinion after seeing these results that plastic hydrometers are perfectly acceptable for use in the hobby. I would say they are even acceptable for use in research. Their precision appears to be well within the range of projects I’ve seen conducted in laboratories. Their accuracy is variable, but with a known (and easily found) correction factor these hydrometers perform quite well." I bet after one year, we looked at the results of 6 refractometer readings, we would have 6 different readings as well for the reasons given in my earlier post. But I agree that if you spend good money for a quality refractometer, carefully clean it after use, diligently follow the calibration procedures, and if you are the type that washes and dries your dishes immediately after use and put them away, a refractometer is for you. Last edited by naesco; 07-12-2009 at 05:05 PM.
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#3
07-12-2009, 05:15 PM
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yup, I fully agree with naesco. While hydrometers can be far from accurate, they are almost always very precise; That is, they are off by the same amount, in the same direction, every time. For example, on a sample of known salinity of 1.025, my hydrometer reads low at 1.018; so I just aim for 1.018 all the time. I have had my hydrometer for three years and recalibrate it every few months but it has yet to change. You also have to keep the things stored in freshwater; I keep mine in a tote that I store topoff water in.
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#4
07-12-2009, 05:18 PM
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Reason why I gave up with the swing arm is one I'd been using for awhile (always rinsing between uses) one day was off 0.006. Didn't drop it, arm swung freely, no signs of damage, etc and it was toast. Can handle a consistent error but not jumps.
Sure a refractometer can go out of cal as well, but just seems they're more sturdier.
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my tank
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#5
07-12-2009, 05:18 PM
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I used a plastic hydrometer for more than 10 years, it was dead on any time I compared it to a refractomer. Then one day, nope, it was way off. They are not reliable, and a refractomer is a more accurate instrument. Or, you could use a lab grade glass hydrometer, these are very accurate.
And paying over $100 for a $50 instrument? Hmm, a foolish Steve and his money...you know the saying  I'm not even sure you can buy one for that much?
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Brad
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