The worlds favourite nutrient meter, The Bluelab EC meter. This super tough high quality design is fully waterproof and requires no calibration, daylight readable blue LED’s and no on/off buttons to worry about. To take a reading, simply place the probe head into your solution for 1-2 minutes to reach the same temperature as your solution and remove from your solution and place back in to take a reading as indicated by the flashing lights. Always rinse probe after use. Main Features EC (0.2-3.6), CF (2-36). Fully waterproof. No calibration required. Auto sense on/off. No external switches or buttons.