Yes and no. Yes, in the fact it measures the "Electrical Continuity" of the "Total Dissolved Solids". But.
It's only accurate to the specific solids within. You can calculate the ppm's if to have a "Key" formula (i.e. foxfarm uses a scale to which you follow)
If you don't know the formula and/or mix formula, it changes the scale used. The more mixes, the farther off the ppm's are.
Let me break it down..
If you mix a two part nutrient setup, and flow theor instructions perfectly, you'll know what you have accurately.
But..
Part "A" might have iron and no Calcium and Part "B" might have Calcium and no Iron. Iron has a higher EC than Calcium.
So it's only accurate if you follow their directions, so you don't throw off the numbers.
If you add Tap Water to the mix, you'll be doing quite a bit of math to figure out you ppms.
EC is easy to check and so better for most grower, but not more accurate.
PPM's are definitely better over all, just harder to measure accurately. Most growers can't afford, or don't know how to measure individual salts.