What do you use to measure salinity?

[jpierson77]

I have a deep six hydrometer that i am currently using. Im thining about getting doemthing that is more accurate, so im looking for a few suggestions. Thanks

[old salty]

I use a refractometer.

[Pomacanthus Rex]

<img src="http://www.jamesinternationalsales.com/science_equipment/refractometer.jpg"/>

[Ti]

refracto

[lessthanlights]

get a refractometer but make sure to get one that adjusts for the temp . . . it's a pain in the arse if you don't

[Xandernfs]

Refractometer....hands down

[garyw68]

Speaking of which. I just got my refractometer about two weeks ago. the line is slanting from right to left. I use distilled water to calibrate it. when i do, the SG shows 0 but the PPT shows 10. Is this normal?...should I return it?

[ChemE]

http://a1272.g.akamai.net/7/1272/1121/20060718130454/www.drsfostersmith.com/images/Categoryimages/larger/lg_14035_FS34702D.jpg
http://www.drsfostersmith.com/Product/Prod_Display.cfm?pcatid=9957&N=2004+113074

$45 well spent since our swing hygrometer varied by up to 0.005 which is totally unacceptable for reefkeeping.

[boxfishpooalot]

All three.Refractometer, conductivity and a swing arm. In terms of accuracy-

1-conductivity(beware of the calibration solution)
2-refratometer(use distilled water)
3-swing arm(dont soak in vinegar over night)

[dkh0331]

The Vee Gee from The FIlter Guys -

http://www.thefilterguys.biz/refractometers.htm

http://www.thefilterguys.biz/images/VEEGEE.jpg

[MarineFiend]

<a href=showthread.php?s=&postid=9157333#post9157333 target=_blank>Originally posted</a> by Xandernfs
Refractometer....hands down

Well really hands on the refractometer to my eye, but oh yes.

Most definitely the Refractometer is the best.

[aninjaatemyshoe]

You should try calibrating the refractometer using a known salinity closer to natural seawater. This can be done using common table salt. The method is shown here http://www.reefkeeping.com/issues/2004-06/rhf/index.php.

The reasoning is that all testing equipment has some degree of error that increases the further you get outside its calibration. So if you calibrate for you're optimum salinity, then you be able to more accurately keep your tank at that level.

[ChemE]

<a href=showthread.php?s=&postid=9157805#post9157805 target=_blank>Originally posted</a> by aninjaatemyshoe
You should try calibrating the refractometer using a known salinity closer to natural seawater. This can be done using common table salt. The method is shown here http://www.reefkeeping.com/issues/2004-06/rhf/index.php.

The reasoning is that all testing equipment has some degree of error that increases the further you get outside its calibration. So if you calibrate for you're optimum salinity, then you be able to more accurately keep your tank at that level.

This is definitely true. Ideally you calibrate an instrument over the range you are interested in measuring that way you don't have to extrapolate. Interpolation is somewhat safe, extrapolation is very dangerous.

[Joshua1023]

Is it just me or does the link to the salinity calibration solution not work? Is that the one where you use a two liter bottle of coke and a few teaspoons of water along w/ a few teaspoons of salt or something like that? I oftern wondered why you had to make up so much solution. Has anyone scaled that down to a lesser amount?

[ChemE]

No, the link doesn't work.

The reason you don't scale it down is that you want it to be as precise as possible and many times the error of an instrument doesn't scale linearly.

[Joshua1023]

gotcha

[drives300]

I use a swing arm that I have calibrated with randy's calibration fluid. I marked a line on it where the calibration fluid registered and I measure my salinity there. It came out to be around 1.029.

[aninjaatemyshoe]

Does it work now? http://www.reefkeeping.com/issues/2004-06/rhf/index.php

[ChemE]

Yes, thanks.

[Icefire]

refractometer have a +-0.001 accuracy which is not bad (0.002 total)

but isn't the float type the more accurate?