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EC/CF Meter's how to use?

Discussion in 'Hydroponics / Aeroponics' started by NFTer, Feb 24, 2011.


    NFTer Member


    Is there a tread where it can explain to me how to use a EC meter correctly?

    How I currently use it:
    1.) Mix feed, adjust PH and fill tanks.
    2.) Give it a minute and test the the EC.
    3.) Give it a day, test the EC, if the EC is higher I PH some water and just add it until I get the EC the same as step 2.

    The questions I have.

    Because I use Root a Gen and Silicon, would this affect the EC reading in the wrong way?
    For example the plants may be taking all the good feed and water out, then the silicon and root a gen is pushing the EC higher?

    I understand how they work (measure salts in the water) but I'm thinking the Silicon and Root a gen will affect it :(

    I clear my tanks every Sunday(Feed), Wednesday(Feed) and Friday(Flush) anyway, but would really like to understand this EC meter better to maybe stop me doing all the work on Wednesdays :)

    Medi 1

    Medi 1 Well-Known Member

    not sure what effecting the ec in a wrong way means. unless the nute has gone bad. firsdt off it takes more than a minuite to set ph and ec. that takes like close to an hour depending on the water quality. then as the plant drinks the numbers will change always or its locked up. some foods effect ec and some dont, and some move ph up or down, most should raise ec though
    you sure your not locked up with ec rising daily
    Tee Five

    Tee Five Active Member

    The thing to know here:

    EC or TDS (Total dissolved solids) is effected only by water soluble elements.

    For example: Your Nutes are water soluble, therefore effect your EC reading.
    While Hydroton is NOT water soluble, therefore will not effect your readings.

    That's how I look at it.
    Medi 1

    Medi 1 Well-Known Member

    has nothing to do with that. only 4 of our nutes in our whole line show on ec, but all are water soluble..
    some reads from a water site

    TDS Meters, Conductivity and Conversion Factors

    Though there is a close relationship between TDS and Electrical Conductivity, they are not the same thing. Total Dissolved Solids (TDS) and Electrical Conductivity (EC) are two separate parameters.
    TDS, in layman's terms, is the combined total of solids dissolved in water. EC is the ability of something to conduct electricity (in this case, water's ability to conduct electricity).
    The only true method of measuring TDS is to weigh residue found in water after the water has evaporated. You know those spots you see on a glass after you wash it and let it air dry? That's TDS! That residue has mass, and it's possible to weigh it, but if you're not in a lab, it can be tricky thing to do. Therefore, we can estimate TDS levels based on the conductivity of the water since the hydrogen and oxygen molecules of the H2O carry almost no electrical charge. The EC of most other metals, minerals and salts will carry a charge. A A TDS meter measures that EC level and then converts it to a TDS measurement. Since different metals, minerals and salts will be more or less conductive than others, there are different conversion factors that can be used.
    ppm (parts per million) is the most commonly used scale to measure TDS (Total Dissolved Solids).
    µS (micro-Siemens) is the most commonly used scale to measure EC (Electrical Conductivity).

    ABOUT TDS and EC

    TDS and Conversion Factors
    EC: There is no conversion for electrical conductivity. (NOTE: The three EC modes in the COM-100 differ only in their ATC programs. The standard EC mode is KCl.)
    TDS - NaCl: 0.47 to 0.50
    TDS - 442: 0.65 to 0.85
    TDS - KCl: 0.50 to 0.57
    (NOTE: Most HM Digital meters use the NaCl factor. The COM-100 has the above three modes, which are user-selected. When converting EC to TDS, the COM-100 uses the non-linear scales, as they would occur in nature, thereby giving you more accurate readings than meters that use linear scales.)

    Converting between different scales
    PPM à µS: The conversion factor of the TDS meter must be known. Once known, the conversion factor should be multiplied by the TDS level. (NOTE: For the COM-100, simply change the mode on the meter. There is no math required.)
    PPM à PPT: Divide by 1000 (1000 ppm = 1 ppt)
    µS à mS: Divide by 1000 (1000 µS = 1 mS)


    What should the TDS of my water be?
    à A TDS level is specific for each application and particular usage. If you are using a meter to test the water pertaining to a particular device, object or operation, contact the manufacturer of that object. For example, if you are using the meter to test the efficacy of a water filtration system, contact the manufacturer of that system for preferred TDS levels. If you are testing the water for a pool, plants, fish, etc. contact a specialist for your specific application.
    What is the difference between µS and µS/cm?
    à There is no difference between µS and µS/cm. µS is a simple abbreviation and is used to save space.
    What is the difference between ppm and mg/L?
    à ppm is an expression of quantity, and an abbreviation for “parts per million.” Mg/L (milligrams per liter) is an expression of weight. Both are used as scales for TDS, but ppm is considerably more popular. There is no conversion between the two. (226 ppm = 226 mg/L)
    What is the difference between a parameter and a scale?
    à A parameter is the characteristic being measured. A scale is a particular range applied to the measurement of that parameter. For example, temperature is a parameter. Fahrenheit or Celsius is a scale.
    Is “EC” a parameter or a scale?
    à “EC” is a parameter. It stands for Electrical Conductivity. There are a number of scales used in EC, most commonly micro-Siemens (µS) or milli-Siemens (mS). For example, if a particular application calls for water with “2.0 EC,” this is an incorrect determination. Most likely, the application is calling for an EC level of 2.0 mS. 2.0 mS = 2000 µS.

    What is NaCl and KCl?
    à These are abbreviations for different conversion factors based on salt content. NaCl is sodium chloride and KCl is potassium chloride.
    Tee Five

    Tee Five Active Member

    Lets not split hairs.

    Most meters use EC to determine TDS. Which is more than fine for 99% of grows.

    But either way--Im not sure why someone would use nutes that don't show up on an EC reading? When all the tried tested and true ones do.
    Of course...Im guessing that all the other nute packages are wrong and they do it right kind -of-answer. But they are the exception to the rule-not the rule.

    NFTer Member

    Thanks for the info guys, but now I am even more confused lol.

    From what I understand then the EC meter is pretty pointless then.

    What I meant in a bad way is the the plants might be taking all the base, grow and bloom from the water but leaving the root a gen and silicon so the ec meter is reading the silicon and root a gen so i think the ec reading is ok if you get me.

    I use genesis feed.

    So how exactly do I use this EC meter, what are the advantages?
    Medi 1

    Medi 1 Well-Known Member

    sorry wasnt trying to be nit picking.

    actualy ec is the true reading and is the type of pen most accurate. i have a Bluer Labs Gaurdian here and it reads all for me ec/cf/tds/ppm. some wont read on certain pens as thats the diff between organics and synthetics.

    NFTer Member

    ahh, I see now, i have a blue labs truncheon, so the liquid silicon and the regen a root wont be measured but the grow, bloom and base will?
    Medi 1

    Medi 1 Well-Known Member

    ok truncheon is a good product. the temp effects the ph more so than the ec and again its all down to the quaslity of the meter as to how the temps effect the real number.
    and the only people that can give an honest answer to why yours read or dont is the nute co to know what was added to the nutrient. if it dosent read on ec dont worry about it, dont adjust what your recipe is to accomodate the ec or ppm.,..use your ec and if your interested in finding the ppm the conversion factor is .5 for most north amewrcan scales and .7 for european...so a 1 ec is 500ppm at .5 ....2 ec is 1000ppm

    heres a chart if you need one...,

    View attachment 1471767

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