Hydrometer Temperature

[DaneAP24]

What should the temp. of my water be when testing with a Hydrometer? And if the temp. is higher/lower than recomended is there some way of subtracting/adding to get a correct reading at that temp. Hope that makes sense but prob. not. Thanx

[wuldiba]

hi, Different types of equipment are often calibrated at different temperatures. hydrometers are often calibrated at 25 degC, whereas refractometers are usually calibrated at 20 degC.

when dealing with hydrometers there are tables available to help with the s.g change in relation to temp. just have a search on the net and you will find them no bother, I have tables here if you want me to send you them?

[121a]

hydrometers are fairly inaccurate.

[DaneAP24]

Yeah, that would be awesome if you could send them. Thanx alot!

[The Propagator]

Hi Dane,

You'll probably want to save up to buy a refractometer and ditch that hydrometer ( even a glass hydrometer ) They don't really compare to the accuracy of a good refractometer. Once you do try a refractometer though you'll see what 121A and I are saying immediately. 1st you will think you calibrated it wrong because it will be so drastically different from your hydrometer but nope it really will be that far off. 3-5 points at least I bet.

[SPS20]

Most hydrometers read most accurately around 78F, if I am not mistaken.

 

Regardless, as others have said, get yourself a refractometer. They are generally more accurate, and you can get one for fairly cheap nowadays. (They used to be expensive as hell, but now the chinese are making them, and they are dirt cheap.)

[d0ughb0y]

hydrometers or refractometers will give incorrect reading if not used properly (like not calibrating).

As for temp, unless otherwise stated in the meter, it should operate in the normal reef tank temp range.

[DaneAP24]

Ok, I am going to look into getting one. Anybody have a preference of brand, make, kind etc. without shattering the bank account. I don't want to go cheap though. Want something good, just not the most expensive.

[The Propagator]

An el cheapo Ebay one I have found to be just as good as a high dollar refractometer actually.

[S197]

just recieved and calibrated my refractometer... heres more stress to my life, my tank reads at 1.028 on the refract but 1.026 on the hydrometer (deep 6) so you can see its .002 off, which isnt horrible, but if your using a hydometer id suggest aiming for like 1.024 on it just incase its inaccurate either way + or - so your within reasonable ranges 1.028 is much to high for me and im just waiting on some new water to finish mixing so I can readjust my salinity.

[d0ughb0y]

just recieved and calibrated my refractometer... heres more stress to my life, my tank reads at 1.028 on the refract but 1.026 on the hydrometer (deep 6) so you can see its .002 off, which isnt horrible, but if your using a hydometer id suggest aiming for like 1.024 on it just incase its inaccurate either way + or - so your within reasonable ranges 1.028 is much to high for me and im just waiting on some new water to finish mixing so I can readjust my salinity.

 

do you get a reading of 1.0 on your hydrometer when you use distilled water? If not, you need to add the offset from 1.0 to the reading you get. Hydrometer does not have a calibration adjustment like refractometer, but it does provide fairly accurate reading if used properly. In your case, you just need to add 0.002 to your hydrometer reading, and it will always give the same reading as your refractometer.

I always get the same reading on my hydrometer and refractometer. sometimes, the hydrometer swingarm will get snagged and a little tap will loosen it and I get the correct reading. I have yet to see anyone succesfully prove Archimedes principle to be incorrect. The refractometer is more convenient to use since I don't have to use as much water to measure SG. Its good to keep the hydrometer around as backup in case the refractometer gets dropped or it grows legs and walks away.