The Milwaukee MC311 EC Controller, 0.0 to 10.0 mS/cm, 0.1 mS/cm, +/- 2% Full Scale, 0.8 to 2.8 mS/cm monitors and controls EC levels. These controllers have a user selectable set point and a visual "Power Activated" LED notification light. Power to the controller box is turned on when the reading is Above or Below (user-selected) the selected set point. The MC311 controllers are ideal for dosing. The user's tank will get the individual attention that it needs. Each unit comes with 12 VDC adapter, mounting kit, probe, probe holder and starter calibration solution for EC. These professional PEC's are especially designed for use with hydroponic systems.