My D-D Seawater refractometer reading low compared to Brine refractometer

Question:

Hello

i have not long got my new d+d short scale reading refractometer and i am having problems with it i tryed the calibration to 20c room temp
dropped some ro on to the it and set to 0 but how do i know my refractometer is at a temp of 20c ? as i tested my salt water and am only getting 1.022 reading yet one of my mates has a aqua medic refractometer and he is reading my salt water at 1.024 S.G can you please help me on getting my refractometer to calibrate right and give me a proper reading

thank you.

Answer:

Ray
The aqua medic refractometer is a brine refractometer and will give a false reading as it is not calibrated for all of the elements in seawater.

Your reading of 1.022 on your seawater refractometer will be correct compared with his 1.024 on a brine version.

To calibrate the temperature of the refractometer you can either leave it in a room at 20C for a couple of hours, measure the air temperature, or put it in a sealed plastic bag and immerse it in some water at 20C.

Set the zero with RO water straight away and then use it normally.

http://www.theaquariumsolution.com/measuring-salinity-and-specific-gravi...

Follow the above link to find out more

I suggest that having read the article you only use the salinity scale and bring your salt level up.

Cheers
Stuart