Understanding Electric Conductivity, TDS and Salinity


Dear all,

Last November, due to the very poor quality of the pH and EC sensors listed in the BOM of the PFC 1.0, I decided to buy a pocket EC/TDS/Salinity tester (Apera EC60 Premium for US$70). I wanted to keep things cheap and simple, and I can use this tester in other situations.

Now that I can measure EC/TDS and Salinity much more reliably (and I measure pH with a basic pH control kit.), the point is: what are the threshold values or points of reference for such variables that I should use to decide when my plants need more nutrients. Or where can I find this information?

@jake, @gordonb, if I check the software of the PFC 2.0, in which I understand the injection of nutrients is automated, will I be able to find the values I am looking for? Do this values depend on the recipe and the crop we are growing?


General Hydroponics has a knowledgebase section on their website about how to use their nutrient and pH adjustment products. These two FAQ pages seem the most relevant to your question:

  1. http://generalhydroponics.com/nutrient-questions
  2. http://generalhydroponics.com/ph-dynamics

You might also like:

  1. Bright Agrotech’s youtube channel
  2. Howard M. Resh’s books: Hydroponic Food Production, or Hydroponics for the Home Grower.
  3. Catalogs from companies that sell seed to farmers.


Many thanks for these answers


Thanks for sharing that!