How do I work out EC?

Hi all, I have been increasing my EC by a little bit here and there over the last month or so on a DWC bucket. But I am not sure if I am at the best EC.

My problem is that my tap water is quite hard and comes out at an EC of 0.80 to 0.85. I am then adding flowering nutes to make the total up to an EC of 2.25 (so about 1.45 of the total is nutes).

My question is, do you include the original water EC or take that away from the total after adding nutes to come up with the total?

I have also read that EC is the PPM divided by 500 or 700 depending on which meter you use......I have no instruction with my meter and it is unbranded so I have no idea which it is.

Any help would be great. Thanks.

I run every thing at about 22 or 2.2 max out at 2.5= 25
There are plenty of conversion tables.... But as a wise man once told me the MAGIC number is 2.2 which is about 1550ppm
hope that helps which includes the value of your water.... which will start or contain TDS`s (totally disolved solids)

THE BEST CONVERSION CALCULATOR IVE FOUND
http://www.4hydroponics.com/convertPPM.htm

There are Micro nutrients in water like calsium, copper, iron etc

Thanks eza82,

Thats cleared part of the problem for me, sounds like I am at a good EC. I am 3 weeks into flower at the moment so will be adding a booster soon.

Just need to know what conversion factor my EC meter uses, if it's 500 or 700....

If you are running a electric meter you need to get EC BUFFER 1.143.... to calibrate( should be done bi weekly), this will also allow you to set at 1.143.

eza82 said:

If you are running a electric meter you need to get BUFFER .07.... to calibrate( should be done bi weekly), this will also allow you to set at .07 ( or is it .70) either way.

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I have calibration fluid (EC 1.42 or something) and you adjust it with a small screwdriver (variable resistor I guess). Other than that it has an on/off button and thats it. I guess this ensures it will be set somewhere near accurate.

Sorry I see what your saying.....

There are three conversion factors which various manufacturers use for data display:

USA 1 ms/cm (EC 1.0 or CF 10) = 500 ppm
European 1 ms/cm (EC 1.0 or CF 10) = 640 ppm
Australian 1 ms/cm (EC 1.0 or CF 10) = 700 ppm

For example,
Hanna, Milwaukee 1 ms/cm (EC 1.0 or CF 10) = 500 ppm
Eutech 1 ms/cm (EC 1.0 or CF 10) = 640 ppm
Truncheon 1 ms/cm (EC 1.0 or CF 10) = 700 ppm

Calculating the conversion factor
If your meter allows you to switch between EC and TDS units, your conversion factor can be easily determined by dividing one by the other.


Conversion factor = ppm / ec.
[Note: ms must be converted to us: One millisiemen = 1000 microsiemens (1.0 ms/cm = 1000.0 us/cm)

According to the chart below:
1.0 ms/cm = 500 ppm (USA Hanna)
1000 us/cm = 500 ppm

Conversion factor = ppm / (ms/cm * 1000)
.50 = 500ppm / (1000us/cm) ]

The answer is your meter's convertion factor and should be a number between 0.50 and 0.72 To improve accuracy, take ec and ppm readings from your res daily for about ten days. Average the conversion factors. The more data points that you use, the closer you will be to finding your true conversion factor.

Loafman said:

I have calibration fluid (EC 1.42 or something) and you adjust it with a small screwdriver (variable resistor I guess). Other than that it has an on/off button and thats it. I guess this ensures it will be set somewhere near accurate.

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Yes............ I thought you meant you wanted to know MANUFACTED variations.......

I hope I have helped!

Seems to me this EC stuff is flawed if you don't know what your conversion factor is! Why is there not a single standard, guess it's just a way of making more money, a bit like VHS and Beta or HD DVD and Blu-Ray.



Thanks for the info, I think I will carry on the way I have been, it seems to be working. If it aint broke, dont fix it!!

Different counrties have different standards...... UK, US, ASIA PACIFIC . So knowing where your meter was manufactured wll be a good start.

eza82 said:

http://www.lenntech.com/unit-conversion-calculator/tds_engels.htm

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Hi eza82, yeah I found a few sites like that, and I am not sure what country spec my meter is so I don't know if my meter reads EC as ppm/500, ppm/640 or ppm/700 as there are 3 (at least) different conversions that different meters use.

Think I will have to buy a meter that has the correct conversion written on it or in the instructions. At least I won't have to be a anymore!

You can work it out with formula from first page...... But also jump on google and find a picture of your meter and specs on it..... or post it in photo we will see if we can id it.

eza82 said:

You can work it out with formula from first page...... But also jump on google and find a picture of your meter and specs on it..... or post it in photo we will see if we can id it.

Click to expand...

I found the receipt for it, so have emailed the company I bought it from to see if they know what it is.

Had a reply from the company I bought it off, and they say it is 1 = 640ppm. So I now know that 2.25 is equivelent to ~ 1440ppm...YAY!!

That does mean my tap water is around 512ppm!! Crikey thats hard!

Thanks for all the help everyone, happy gardening!