HI981413 Nutrient Dosing System for Nutrient Solutions and Irrigation Water HI981413 Nutrient Dosing System is engineered for maintaining the concentration of fertilizer in the nutrient solution used in hydroponics and irrigation water. The nutrient concentration in the water used for irrigation is critical for the successful propagation and growth of plants. The HI981413 uses an amperometric conductivity sensor for measuring the amount of fertilizer in the solution. The meter can be programmed to display results as EC (electrical conductivity) or as TDS (total dissolved solids). The EC results are displayed as mS/cm while TDS is displayed as ppm with a selectable conversion factor from 0.45 to 0.99. The HI981413 was developed to be an inexpensive solution for the horticulturist to maintain the ideal fertilizer concentrations at all times. Simply insert the probe and injection valve in-line with the recirculation pump and provide the chemical to be dosed.