The OxyGuard hand-held refractometer is a small refractometer designed to measure the salinity of sea water and saline solutions of similar concentration. It has a scale of 0-100 ppt, with 1 ppt scale divisions, enabling the direct determination of salinity in water that contains dissolved salt and little or no other dissolved solids.
As all OxyGuard instruments it is accurate and easy to use. Open the flap, place one or two drops of the water you want to measure onto the window, close the flap, hold the refractometer towards a bright light and observe the reading through the eyepiece. The eyepiece can be adjusted to suit the eye of the user. Wipe the refractometer dry with a soft cloth after use.
The right-hand scale shows the salinity in parts per thousand, the left-hand scale shows the specific gravity of the solution. The illustration below shows water with no dissolved salt.
Adjust the zero as necessary, using tapwater or distilled water - adjust to zero using the small screwdriver provided to turn the zero screw, which is found under a protective cap.
The refractometer is temperature compensated for normal ambient temperatures.