# Could someone please explain what EC is?



## 420benny (Jan 30, 2009)

I am searching for a meter for hydro. I have been checking out Hanna products. They keep mentioning EC/TDS. Are they the same thing? I know EC stands for electrical conductivity, but that's as far as I can figure out. I tried a search and no one talks specifically about EC. In none of the grower journals do folks mention it, only ph, ppm and temp


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## umbra (Jan 30, 2009)

EC and ppm are in essence the same thing. EC is measured by taking an ohm meter and measuring the resistance or lack thereof, of water also called electrical conductivity. The parts per million is more commonly used in usa and ec in europe. A certain ppm will equal a certain ec. The ppm meters actually measure ec and then convert to ppm. Does that make sense


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## bud.uncle (Jan 30, 2009)

> *What is the difference between ppm and EC?*
> Total Dissolved Solids (TDS) is the best measurement of the nutrient concentration of a hydroponic solution. To estimate TDS, one can use a meter that measures the Electric Conductivity (EC) of a solution, and convert the number to TDS in parts per million (ppm). Many meters will do this conversion.
> 
> Total dissolved solids (TDS) is typically expressed in parts per million (ppm). It is a measurement of mass and determined by weighing, called a gravimetric analysis. A solution of nutrients dissolved in water at a strength of 700 ppm means that there are 700 milligrams if dissolved solids present for every litre of water. To accurately calculate total dissolved solids (TDS), one would evaporate a measured filtered sample to dryness, and weigh the residue. This type of measurement requires accurate liquid measurement, glassware, a drying oven, and a milligram balance. Example: 50 ml of the 700ppm solution would leave 35 mg of salt at the bottom of a crucible after drying.
> ...



hxxp://www.420magazine.com/forums/how-grow-marijuana/71813-what-difference-between-ppm-ec.html


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## Tater (Jan 30, 2009)

Always go with EC if you can or if you can't figure out which formula your probe maker is using to convert EC to PPM and then reverse it so you can get a true reading.  PPM readings are pretty useless, I liken them to MPG.  The amount of possible variables affecting the outcome of either tend to give you results that mean a little less than nothing.


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## 420benny (Jan 30, 2009)

Thanks bud.uncle for a very informative answer. That is exactly what I needed. Tater, thank you too. Just looking at ppm seems to be an "about right" rather than an exact number.


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## Tater (Jan 30, 2009)

Pretty much, as long as you don't switch meters and find what works then stick with it you'll be golden.


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