hydrometer calibration

[jng3]

What temperature is the deep six hydrometer calibrated at and what is the formula to adjust the reading for temperature.
Thanks!

[obtusewit]

68 - 85 °F is what SeaTest, Deep Six, and eSHa Marinomat claim. The SeaTest and the Deep Six do a fair job of temperature correction, but in fact slightly overcorrect.


Using a standard measured to be S=35 ± 0.5 by conductivity, the Deep Six swing arm hydrometer got readings of S=32.5 ± 0.5 at 81 °F and S=32 ± 0.5 at 68 °F. Using the SeaTest I got S=34.5 ± 0.5 at 81 °F and S=34 ± 0.5 at 68 °F.

I did not try multiple Deep Sixes Or Sea Tests but I am certain there is some variance between the same brand.

Conductivity is the most accurate follwed by a refractometer. Your best bet is to find someone with a refractometer and compare your Deep Six with that.

[matt]

I really would not trust any of the plastic swing arm hydrometers. They're notoriously inaccurate. You can calibrate it with a big glass hydrometer or a decent refractometer. Tropic marine makes a decent glass hydrometer.