Salinity Mismatch

[MDProuty]

I received my Hanna testing equipment today, a major upgrade from a handheld hydrometer and my API test kit! The first parameter I checked was salinity. Hanna provided a reading of 1.0265 SG at 80.0 F, while my manual measurement technique showed salinity of 1.024 SG at 80.6 F (temperature based on Current temperature probe). This seems like a huge difference. My gut feeling says to trust in Hanna; however, I’ve been using the handheld hydrometer for over a year now. What do y’all think?

I have two other temperature readings in my tank showing 78.8 F based on my newly installed Seneye and 81 F based on my heater’s temperature sensor. Also, I did perform a calibration prior to using the Hanna salinity tester.

 

[Spare time]

I would bet on the hanna over the hydrometer (which are not known to be dead accurate)

 

[taricha]

I love my swing arm hydrometer (Instant Ocean). It gives very tightly repeatable results, BUT the labeled values don't match, and that's pretty common. So to really get the most out of a swing-arm, you need to make a salinity standard. See this from Randy
http://reefkeeping.com/issues/2004-06/rhf/index.php

and then mark the hydrometer to your own standard.

(without that calibration, I'd bet the hanna is closer.)

 

[MDProuty]

I love my swing arm hydrometer (Instant Ocean). It gives very tightly repeatable results, BUT the labeled values don't match, and that's pretty common. So to really get the most out of a swing-arm, you need to make a salinity standard. See this from Randy
http://reefkeeping.com/issues/2004-06/rhf/index.php

and then mark the hydrometer to your own standard.

(without that calibration, I'd bet the hanna is closer.)

That makes a lot of sense. I never thought to calibrate my swing arm hydrometer. I'm going with the Hanna results.

 

[EMeyer]

taricha makes a great point about calibration, which is a necessity for any method of reading salinity.

I personally prefer any device with a digital readout, rather than a gauge. Reading on a physical gauge automatically limits you to the precision of the ticks. 1.024 or 1.025, nothing in between. At BEST a person could estimate the arm is halfway in the middle and guess that perhaps its 1.0245. But really, that'd be a guess.

Thats not even getting into how the big fat end of the swing arm covers the full range from 1.024 to 1.025, so a person has to guess where the middle of the swing arm is.

In the end, I find that such a device can give both accurate and repeatable results but the resolution is very low. Incapable of measuring small differences. Does that matter? Probably not at all Just expressing why I dislike swing arm hydrometers so much.