question about my blue lab ppm meter

[Buzz]

i have the wand
it is said to be the best out there.
but here is my question
it has 2 sides to it EC PPM and CF PPM what side should i be reading???
anyone got an info on this for me?

 

[Stackin Paper]

I've found if you're in the u.s they normally use ppm but here in uk we use ec ,cf

 

[Slick]

EC is the measure of the electrical conductivity within a liquid solution and my understanding of it is that EC is the most consistent measure overall; EC is the basis for which PPM (parts per million) is determined as PPM can only ever be 100% accurate in a lab.

Hope that helps.

Edited for grammar.