Hanna Instruments
On demand
Hanna Instruments digital refractometer for salinity and specific gravity of seawater, one model.
HI96822
This Hanna Instruments digital refractometer measures salinity and specific gravity of seawater.
Marine organisms tolerate a narrow salinity band, and in a closed system salinity only rises, because water evaporates and salt does not. Topping up with fresh water is a daily judgement that should be made on a number.
Light bends by a different amount depending on how much is dissolved in a liquid. A refractometer measures that bend and converts it to a concentration scale. It needs one or two drops, gives an answer in seconds, and has no reagents and nothing to consume.
A digital instrument compensates for temperature automatically, which is the difference that matters: refractive index shifts with temperature enough that an uncompensated reading in a warm room is simply wrong.
Specific gravity readings are meaningless without their reference temperature; a digital instrument compensating automatically avoids the most common mistake in the hobby.
Supplied as one model.