Refractometer readings in %

Thadius · 08-30-2006, 05:43 AM

Hey guys

Just got my new refractometer in the mail (and pH probe in all it's uncalibrated glory) and took my first reading. It gave me right on 4% on it's 'salinity' scale. After an hour or two of probably needless googling on ppt sg and % conversion tables or calculators I think I've come up with what the 4% reading I got means ?

4% = 40ppt (parts per thousand) meaning my aquarium water is around 1.028 sg... The specific gravity I'm not sure about because it's temp dependant and the refractometer has ATC (Auto Temp Compensation). For the SG I want my tank to be (1.026) I'll need a 35ppt reading (3.5%) on my refractometer. I've been keeping my tank at 1.026 with a swingarm hydrometer which I always knew would be far from accurate, and by the looks of it the reading of 1.026 it's been giving me is probably more like 1.028 or possibly even higher

I'm just wanting to confirm what I think my little bit of research is telling me about the readings on my refractometer.

Cheers

veriann · 08-30-2006, 11:44 AM

i may be an old school idiot, although i have asked my LFS to provide me with a $300+ refractometer i have not had a chance to use it yet, in saying that, i have always looked after my hydrometer with white vinager for calabration. & challenge any reading thus far i have been given!
i have no doute a refractor is king,> so many people cant be wrong! but in saying that a hydrometer even for budgeted can be of use regardless!
it would prob be a good idea to define the process of a refractormeter before we hear about it on reefcast people!?

***Rob*** · 08-30-2006, 11:51 AM

this is a good point.
i have not seen one that reads in % so i cant verify the conversion.
but if it has ATC then its accounting for that and your reading is likely accurate.

calibration of a refractometer is simple, just place some RO water on the lens and it should read right at the 0 line or 1.000 SG.

as far as the swing arm hydrometer, i agree with V, if you start by seasoning it properly, and keep it clean, they can be relatively accurate, i think the accuracy is the refractometer is more in the ATC and the consistency, where a hydrometer can vary more.