Bluelab Guardian MonitorAdjustable brightness display. Large easy-to-read, plant-safe green LED displays. Selectable values for conductivity and temperature. Simple push button pH calibration system. No calibration required for conductivity and temperature. Silent alarm for both high and low settings. Settings retained when power lost (non-volatile memory). Temperature compensation. An international power supply. Water-resistant design. 2 year Bluelab® Guarantee (6 months on probe).