Description Hy-Gen Conductivity Standard Fluid To ensure accurate readings, it is essential to calibrate your Electrical Conductivity (EC) or TDS (Total Dissolved Solids) meter with Quality Scientific Grade HY-GEN Conductivity Calibration Solution regularly. The Electrical Conductivity (EC), measured in milliseimens (mS/cm2), Conductivity Factor (cF) or parts per million (ppm) is the measurement of available nutrient in the solution. The conductivity increases as nutrient increases. Distilled or deionised water will gave a near zero reading. As a general guide for hydroponics: 1mS/cm2 = 10 cF = 700ppm. Nutrient requirements vary from plant to plant; therefor the ideal conductivity varies from plant to plant also.