Hi Silver,

Well TDS is short for "Total Dissolved Solids" which is read in Parts per million = PPM. EC is just a different way of checking TDS each meter comes with instructions. You can get a Sharp TDS meter for around $80 and then just get the calibration solution to go with it. Just do a web search for "Sharp TDS meter's for sale" and you'll find lots of place to get one.

Herbus