What is the difference between TDS and EC?
They are both measurement values for knowing the concentration of soluble fertilizers in a nutrient solution. Just as distance can be measured in miles and kilometers, nutrient strength can be measured in different values. TDS is short for Total Dissolved Solids and the units are in parts per million (ppm). This is the value that most North American hobby gardeners are familiar with and almost all of the testers here measure in. EC is short for Electro Conductivity and the units are milliSeimens per centimeter (mS/cm). In commercial agriculture this value is now represented as just EC whereas 1EC = 1000mS/cm. Nutrient testers take their measurements by first reading the actual electro conductivity of the reference solution (more soluble salts = higher conductivity) and displaying that value as either EC in mS/cm or converting the value to read TDS in ppm. Conversions: Different salts have varying effects on electro conductivity in solution.
