How do I measure my EC?

Now I've been getting these cool feeding schedules and can't wait to try out the levels that are recommended to me. Regardless of any of that, I see slot of it talking about EC and EC levels.. Now I looked up that it means electrical conductivity. And that it apparently is a better means of measure the ppm or ph?

Regardless, what exactly is it replacing/used for? And how to achieve figuring out Desired levels? Thanks to any constructive criticism or advice.

http://www.dutchmaster.com.au/?language=english&page=growers_guide&topic=ppm_ec_cf_conversion

It depends on your meter as to how ppm is converted, youll need to find that out first then follow this simple conversion chart....

Thank you