It is essential when growing with a hydroponic solution to know the strength of the solution before feeding your plants as well as during growth. This is easy when using Truncheon! To take a reading of your solution, you just have to place the probe head in the solution for 1-2 minutes to reach the same temperature of your nutrient. Remove it from the solution and return it to taking the reading when indicated by the flashing lights. Rinse the probe after each use in fresh water and clean once a month to prevent the Truncheon Nutrient Meter from losing accuracy