Electrical Conductivity (EC) is the ability of a solution to conduct electric current. Therefore conductivity is used to measure the concentration of dissolved solids which have been ionized in a polar solution such as water. In hydroponics, Electrical conductivity (EC) indicates the number of nutrients available for your crops to absorb. The higher the EC reading, the greater the availability of nutrients. 

More isn’t always better when it comes to nutrients, though. A full-strength nutrient formula has an EC of approximately 1.8 mS/cm^2, but young plants do a better job of absorbing water and nutrients in a mild formula with an EC of 1.2 to 1.6 mS/cm^2. By using an EC meter, hobbyists and commercial growers can eliminate the guesswork and prevent the common mistake of over-fertilizing. 

An EC meter displays nutrient levels in mS/cm^2 or µS/cm^2 (1 mS/cm^2 = 1000 µS/cm^2). Some growers, however, prefer to measure nutrient levels in terms of Total Dissolved Solids (TDS). TDS meters display results as parts per million (ppm). TDS is converted from EC with a typical conversion factor of 700:1. This ratio means that a single unit of EC equals approximately 700 ppm. Other TDS meters use a conversion factor of 500:1. For growers in the U.S., it is safer to rely on the 700:1 conversion factor. Fortunately, with Apera's meters, the TDS conversion factor is always customizable.

EC readings make it simple for growers to monitor and adjust nutrient levels. If the EC level rises above 1.8 during the vegetative growth stage, water can be added to the reservoir to lower the EC. If the EC drops below 1.2, more fertilizer is the answer. 

For optimal plant growth and yield, monitoring EC levels should be part of a daily routine.