What is the difference between EC and TDS?
There’s a lot of disagreement over the relative merits of measuring Electrical Conductivity (EC) as opposed to Total Dissolved Solids (TDS), so I’ll do my best here to explain the debate in the simplest terms possible. Both measurements are used by indoor gardeners to determine the strength of a hydroponic nutrient solution, and either one can deliver the information a gardener needs to make adjustments and corrections in the reservoir. The source of all the trouble is that while the information gardeners need to optimize plant growth is the TDS of the nutrient solution in Parts Per Million (PPM), no method exists to measure TDS directly. Every meter out there only measures the EC of a liquid, usually in milliSiemens (mS) or microSiemens (µS). “Hey, wait a minute,” you say, “I’ve got a TDS meter, and it works great!” Well, that may be, but really that instrument is measuring EC, and then converting it into TDS using a standard algorithm. “So why wouldn’t I want that?” you ask. This is
