There are the digital or the analog version of the salinity refractometer.
Analog refractometer has a wide salinity range from 0 to 100 ppt.
Digital refractometer can show the measurement in second. It can also convert salinity between:
a) Practical Salinity Units (PSU)
b) Parts per thousand (ppt)
c) Specific Gravity (S.G.)
The salinity refractometer comes in a box and consists of a eye dropper and a refractometer.
The front plate of the refractometer open up to show a blue prism.
Take a water sample from your volcano shrimp (opae ula) tank.
Place 1 to 2 drops of water sample on the blue prism.
Close the cover and stand below a light.
The refractometer need a light source to reflect the reading.
Look into the eyepiece of the salinity refractometer. Make sure you are facing a light source.
When the viewing angle is incorrect, the light cannot reflect into the prism properly. You will see a white salinity chart.
But if the viewing angle is correct, you will see a blue and white salinity chart.
There are 2 salinity chart on a salinity refractometer.
The right chart shows the salinity reading in ppt (Parts per thousand). The left chart shows the specific gravity (S.G.) reading.
The correct measurement is taken on the blue and white divider line.
This reading here shows a salinity of 1.015 S.G. or 20 ppt.