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Thread: EC Meters Tutorial

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    Default EC Meters Tutorial

    Ok guys I've decided to write this tutorial on the correct use of EC meters in hydroponics.
    I know from reading diaries/posts on here that it is a subject that comes up regularly so hopefully this will address most of the issues.

    Let's start at the beginning, EC refers to the electrical conductivity of an object, in our case the EC of our hydro reservoir.
    The EC is a measure of the nutrient solutions ability to conduct electricity which is useful because it depends on the amount of nutes so more nutes means higher EC and vice versa.
    Much of the confusion surrounding EC is caused because there are three different units of measurement that are used

    1 )siemens per meter s/m or sm-1
    2 )parts per million ppm
    3 )total dissolved solids tds

    The last two units are defunct and soon to be assigned to the dustbin of history while the first is the internationally recognized unit adopted by the scientific community so I will only be dealing with that.
    OK as we have seen the basic unit of EC is the siemen per meter, i.e. it's ability to conduct electricity over a known distance.
    Now that is all fine and dandy but for our purposes it can be a bit unwieldy because we are measuring very, very small readings.
    For example if I go and take a reading from my res just now my digital EC meter might say
    "123" with a small "x10" symbol flashing in the corner. So what does that mean?
    Well first off you have to be aware that most hydro EC meters are calibrated to give readings in micro siemens per meter (us/m or usm-1) not siemens per meter.
    This is shown by a "us" symbol above the display and most digital hydro EC meters will have this symbol.
    So in this example my meter is telling me I have a EC of 123x10 micro siemens per meter or 1230 us/m.
    OK great I have a reading from my meter in units I understand so how does this relate to my grow?
    If you are a hydro grower then you will be familiar with feeding schedules like the one I use for my canna aqua nutes.
    Pay attrention to the recommended EC levels on the right hand column of these table.
    You'll see numbers like 1.2-1.4 so you probably wonder how that relates to my previous reading of 1230 us/m?
    If you look closely at the bottom of the table you'll see that recommended maximum EC is given as 2.8ms/cm or 2.8 milli siemens per centimeter so what does this mean?
    This tells me that all EC values in the table are given in milli siemens and not micro siemens so we have to take that into account.
    2.8ms/cm =2.8 x10-3 siemens per centimeter = 0.0028 siemens per centimeter, done by moving the decimal point 3 places to the left as indicated by the "milli" prefix.
    Another thing to notice is the move away from siemens per meter to siemens per centimeter but this doesn't matter because the measurement is still taken over a known distance and this is already dialled into you EC meter so don't worry about it just concentrate on the siemens value.
    Basically the move away from siemens to milli siemens is done merely for convenience, it's easier to write 2.8 ms than 0.0028 s.
    So basically what we want to do is convert our meter reading in micro siemens into the more commonly used milli siemens. How do we do that.
    OK back to the example.
    I have a reading of 1230 us that I want to express in ms.
    1230 micro siemens = 1230 millionths of a siemen = 1230x10-6 = 0.001230 siemens done by moving the decimal point six places to the left as indicated by the micro prefix.
    0.001230 siemens = 1.230 milli siemens done by moving the decimal point 3 places to the right.
    So now I have my answer in terms I can work with, my EC is 1.23 milli siemens.
    So that is what all the maths boils down to in the end, you will be converting from micro siemens to milli siemens to tie in your readings with the feeding guides and all you have to do is move the decimal point 3 places to the left.
    for example
    1)meter reading = 500 = 0.5 milli siemens
    2)meter reading = 100 x10 = 1000 micro siemens = 1.0 milli siemen
    3)meter reading = 190 x10 = 1900 micro siemens = 1.9 milli siemen

    Here is a useful online converter you migh find useful
    http://www.translatorscafe.com/cafe/...mens-%5BmS%5D/

    Remember always pay attention to the flashing "x10" indicator if it appears!
    Comments and questions are welcome.

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  3. #2
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    thanks mate..you took a good long time typing that out and I appreciate all that work..

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    Unhappy

    Hi mate thanks for the tutorial but my head hurts trying to work it out as i'm a bit stupid at this kind of stuff,my problem is i bought a ADWA AD204 EC pen from grotec and it measures in millisiemens which i don't understand,i put up a pic for you so hopefully you can understand what i mean,i'm used to reading the EC measurement on a bluelab which is pretty straight forward but what i'm wanting to know is how i convert from millisiemens to EC.

    Am i right in thinking that the reading in this pic would be 0.1 in EC but nearly 0.2.i know it says 0.19 and this is whats confusing me,when measured in millisiemens would 0.2ec be 0.20.
    Thanks.

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    1 )siemens per meter s/m or sm-1
    sounds like a forensic report on a gang rape crime scene.
    if you're retired or you ain't got a job and you ain't growing and smoking weed ,i don't know what the fuck you are doing!

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    cheers wert but not the answer i'm looking for mate.

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    Quote Originally Posted by Cannalover View Post
    Hi mate thanks for the tutorial but my head hurts trying to work it out as i'm a bit stupid at this kind of stuff,my problem is i bought a ADWA AD204 EC pen from grotec and it measures in millisiemens which i don't understand,i put up a pic for you so hopefully you can understand what i mean,i'm used to reading the EC measurement on a bluelab which is pretty straight forward but what i'm wanting to know is how i convert from millisiemens to EC.

    Am i right in thinking that the reading in this pic would be 0.1 in EC but nearly 0.2.i know it says 0.19 and this is whats confusing me,when measured in millisiemens would 0.2ec be 0.20.
    Thanks.
    mate as I said before lol..if its 0.50 on your EC PEN thats half of 1.00 so if you want it to be 1.2 just ignore the last number of 1.20 so it will end up as 1.2 EC

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    Red face

    Mate i did say i was stupid,thick as shit sometimes maybe i smoke too much pakistan ryderi get it now mate,so if my EC was 1.2 it would show 1.20 on my meter yes

    Sorry if i pissed you off up2nogood just trying to get a grip of this meter thats all its more complicated than bluelab.

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    Quote Originally Posted by Cannalover View Post
    Mate i did say i was stupid,thick as shit sometimes maybe i smoke too much pakistan ryderi get it now mate,so if my EC was 1.2 it would show 1.20 on my meter yes

    Sorry if i pissed you off up2nogood just trying to get a grip of this meter thats all its more complicated than bluelab.
    you didn't piss me off at all mate..lol..so you know how to use it now? and yes if it showed 1.20 it would be 1.2

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    Wink

    Thankyou mate glad i didn't pyo yeah got it sorted now just needed it verifying thats all.

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    sorry cannalover was just trolling.
    in answer to your q's they are the same as nogood says. the decimal point stays in the same place.

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    Thankyou mate glad i didn't pyo yeah got it sorted now just needed it verifying thats all.
    Hi cannalover I'm sorry I wasn't here to help you in person mate but wert's and nogood's advice was good so hopefully you understand how to read your EC meter correctly now?
    If you or any one else has any trouble come here or PM me and I'll be glad to help.
    Thanks to ever one for the interesting contributions!

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    Thread stuck !

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    Quote Originally Posted by blurry-vision View Post
    Thread stuck !
    Thanks so much blurry you have saved my patience and my worn out fingers m8!

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    Thanks for the tutorial... So much info, must have taken ages!

    I have a quick question, my autos are flowering (3 of them in a 30L tank wilma) and ive just given them a nice big feed, its taken my ec up to 1.8 though..... is it ok to just leave it like that or should i add some more water? sorry for such a crap question... im one of them nubies ;-) ... and abit annoying.

    Imogen
    Talk about your plenty Talk about your ills, One man gathers what another man spills.

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    what was the ec before you added the nutes?

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    Quote Originally Posted by Imogenrose12 View Post
    Thanks for the tutorial... So much info, must have taken ages!

    I have a quick question, my autos are flowering (3 of them in a 30L tank wilma) and ive just given them a nice big feed, its taken my ec up to 1.8 though..... is it ok to just leave it like that or should i add some more water? sorry for such a crap question... im one of them nubies ;-) ... and abit annoying.

    Imogen
    It's impossible to tell you without more info about your grow. In general if your EC is falling and your pH is rising everything is OK and plants are feeding.
    If however your EC is rising then that is over feeding and you can expect nute burn to follow so you must adjust EC down until you get a natural daily fall in EC.
    My advice is to go to this thread and ask for a mentor to teach you the ropes there are lots of good hydro growers here.
    http://www.thctalk.com/cannabis-foru...uests-are-here..
    Last edited by illearth67; 20-01-12 at 01:17 AM.

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    thats funny lol

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    EC is something im still to get my head around, how important is the EC level when growing ??

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    Quote Originally Posted by Thadeejay View Post
    EC is something im still to get my head around, how important is the EC level when growing ??
    Hi m8 if you are growing in soil then you can forget about EC but for active hydroponic systems like Waterfarms, Wilmas or Oxypots it's essential to keep track of your EC to ensure your plant is being fed correctly.

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    Thanks for that tutorial. Its the first one out of many that I have read that I actually understood. I can now read my ec meter properly.

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