Bluelab Truncheon EC Meter The world's favourite conductivity meter. Simply brilliant, brilliantly simple!It is essential when growing with a hydroponic solution to know what the strength of the solution is BEFORE feeding plants and DURING growing.This is easy with the Bluelab Truncheon Nutrient Meter!To take a reading of the solution, simply place the probe head into the solution for 1-2 minutes to reach the same temperature of the nutrient. The reading is indicated by the flashing lights. Calibration of the meter is not required.Meter length: 40.7cm or 16 1/32 in Features Fully waterproof Auto on/off function No calibration required Daylight readable blue LED's Battery operated No buttons, switches or knobs Provided with EC, CF, ppm 700 and ppm 500 scales