EC is referred to as electrical conductivity of a nutrient solution. It is a measure of ion concentration in the solution. Expressed in terms of mS/cm. For the sake of simplicity, the higher the EC, the stronger the nutrient solution is.
In the fertiliser solution, EC reflects the relative ion concentration of nitrogen (N), phosphorous (P), potassium (K), that is either not the accurate or specifiying the exact type of salt ion present. EC of any nurient solution is regarded in terms of EC or mS/cm.
An ideal EC for a solution can be given as 1.5 EC or 1.5 mS/cm. Any less than that of optimal EC value is indicative of nutrient deficiency, especially low value of N. The higher the EC is, the harder it is for a plant to absorb the water and salt ions it needed from the nutrient solution. And even higher EC leads to salt toxicity leaf burn.
EC is both simple to use and universal. For example, 1.3 EC will always be 1.3 EC – in every country, in every situation and with every meter. There really isn’t any better measurement.