The BL983324 is a compact, panel mounted, process controller for measuring total dissolved solids (TDS) of a process stream that is within the 0.0 to 49.9 ppm (mg/L) range. The device features a large LCD with protective cover. Users may choose from automatic or manual dosing modes. When in automatic mode the dry contact relay is activated when a reading is above the set point. The relay can be used to supply power to a dosing pump or a solenoid connected to a valve. The BL983324 can also be used to monitor the quality of water produced from ion exchange, reverse osmosis (RO) or distillation.