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UnderMirkwood

EC and TDS

I am about to start a my first hydro grow and I have everything ready to go but I just have one question...Which system do I use to convert EC to TDS? Do I multiply the EC by 5 or 7 to get the TDS? I have the GHE Flora 3 part nutrient and their feeding chart is for TDS so just want to clarify which scale I should use. The EC straight from the tap is 0.0 btw.

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google image search "ec to ppm chart" but as a rule for every 50ppm TDS that equals 0.1 ec

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Thanks for your reply Golden Syrup, I have downloaded a conversion chart but it gives two different readings. The table has 5 columns, the first is mS/cm2 (Millisemen per cm2), the second is EC, the third is CF, the 4th is PPM 500 TDS, and the last is 700 PPM TDS.

 

So what I meant by my original question was do I use the 500 PPM Column or the 700 PPM Column? As an example; an EC reading of 0.5 could be interpreted in two different ways depending which column I look at, the 500 PPM Column gives a TDS of 250, while the 700 PPM Column gives a TDS of 350.

 

To confuse matters further, the GHE Feeding Schedule I downloaded states that in order to find the PPM value I should multiply the EC by 1000 then divide by 2.

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1 hour ago, UnderMirkwood said:

To confuse matters further, the GHE Feeding Schedule I downloaded states that in order to find the PPM value I should multiply the EC by 1000 then divide by 2.

That is 500 scale, EC: 1.0 * 1000 / 2 is 500 ;)

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Cheers Dude, muchly appreciated 

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Mostly people use the 500 scale. Some devices use 540, some 700 but if it is not stated, it is usually safe to assume people are using the 500 scale.

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