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Thread: tds calibration

  1. #1
    Extreme Koi Member Rank = Yonsai sff's Avatar
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    tds calibration

    hi i have some tds calibration fluid marked as 1413 us/cm is this the same as ppm thanks shaun



  2. #2
    Extreme Koi Member Rank = Supreme Champion Davej's Avatar
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    Simple answer is, I think no..

    What are you trying to calibrate?

    Dave

  3. #3
    Extreme Koi Member Rank = Yonsai sff's Avatar
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    tds meter that reads ppm dave

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    Extreme Koi Member Rank = Supreme Champion Davej's Avatar
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    The 1413 is an EC reading in siemans units.. There is normally a conversion into TDS ppm..

    From memory most of the hanna units are dual EC /TDS and the calibration is done in EC mode, the 1413 is I think a standard hanna fluid.. I think in the 700-800ppm range...

    I tend to calibrate at ppm levels more closely aligned to those that the unit will be measuring so start with a solution with 342ppm and then cross check with solutions at a lower level to check the scale/slope is accurate.

    Dave

  5. #5
    Extreme Koi Member Rank = Yonsai sff's Avatar
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    thanks dave where do you get your calibration fluid from this was of absolute koi only one they did will have to find the conversion

  6. #6
    1413 uS/cm = 904 ppm TDS


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  7. #7
    Extreme Koi Member Rank = Supreme Champion Davej's Avatar
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    Quote Originally Posted by JohnKitching View Post
    1413 uS/cm = 904 ppm TDS


    Sent from my iPhone using Tapatalk
    I think it depends on which conversion factor John, seems to all depend on the scale the meter uses in ppm mode?

    "NaCl" "442" or "KCl"

    For the HTM units then NaCL solution.

    Calibration Solutions

    For a Hanna unit the 1413uS or 1500ppm, depends on the model of meter which solution is recommended.. Found a whole stack of 1413uS sachets testimony of ordering the wrong solutions when I ran Hanna TDS meters..


    Dave

  8. #8
    Actually, it depends what's in the sample, uS/cm is a direct measurement of resistance.
    You can convert resistance to TDS using a standard (which I did) but at the end of the day if your calibration solution of xxx TDS has a TDS made up of different molecules to that making up your pond then the calibration is pretty meaningless.


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  9. #9
    Extreme Koi Member Rank = Supreme Champion Davej's Avatar
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    Quote Originally Posted by JohnKitching View Post
    Actually, it depends what's in the sample, uS/cm is a direct measurement of resistance.
    You can convert resistance to TDS using a standard (which I did) but at the end of the day if your calibration solution of xxx TDS has a TDS made up of different molecules to that making up your pond then the calibration is pretty meaningless.


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    Sorry you have lost me..

    I can see the conversion tables from EC on the net.

    Which standard did you use? and is it not meter specific?

    I cant get near 900ppm for 1413 fluid yet I can get a reasonable fix at 342 and 1500ppm

    Dave

  10. #10
    The conversion isn't meter specific but it is chemistry specific.


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  11. #11
    Extreme Koi Member Rank = Supreme Champion Davej's Avatar
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    Quote Originally Posted by JohnKitching View Post
    The conversion isn't meter specific but it is chemistry specific.


    Sent from my iPhone using Tapatalk

    Can see from the Lenntech site where you get 904ppm.

    But does not the conversion that is used depend on the meter and the conversion the meter uses in displaying ppm?

    My understanding is that all TDS meters measure EC but have different conversion factors to give a ppm reading.. so stick a sample of 1413 in one that uses 442 and you will get a different number ppm than one that uses Nacl?

    Dave

  12. #12
    How about this then:

    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 liter 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.

    Electrical Conductivity (EC) is expressed in siemens per centimeter (s/cm) or milliseimens per centimeter(ms/cm). It can be determined with an inexpensive hand held meter. Nutrient ions have an electrical charge, a whole number, usually a positive or negative 1, 2, or 3. EC is a measurement of all those charges in the solution that conduct electricity. The greater the quantity of nutrient ions in a solution, the more electricity that will be conducted by that solution. A material has a conductance of one siemens if one ampere of electric current can pass through it per volt of electric potential. It is the reciprocal of the ohm, the standard unit of electrical resistance. A siemens is also called a mho (ohm backwards).

    For convenience, EC measurements often are converted to TDS units (ppm) by the meter.

    The meter cannot directly measure TDS as described above, and instead uses a linear conversion factor to calculate it. Everyone’s nutrient mix is different, so no factor will be exact. The meter uses an approximate conversion factor, because the exact composition of the mix is not known. Conversion factors range from .50 to .72, *depending on the meter manufacturer, which do a good job of approximating a TDS calculation from the meter’s measurement of EC.

    * All ppm pens actually measure the value based on EC and then convert the EC value to display the ppm value, having different conversion factors between differing manufacturers is why we have this problem communicating nutrient measurments between one another.

    EC is measured in millisiemens per centimeter (ms/cm) or microsiemens per centimeter (us/cm).

    One millisiemen = 1000 microsiemens.

    EC and CF (Conductivity Factor) are easily converted between each other.
    1 ms/cm = 10 CF

    "The communication problem"...
    So again, the problem is that different ppm pen manufacturers use different conversion factors to calculate the ppm they display. All ppm (TDS, Total Dissolved Solids) pens actually measure in EC or CF and run a conversion program to display the reading in ppm's.

    There are three conversion factors which various manufacturers use for displaying ppm's...

    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.

    Place the probe in the solution and read TDS in ppm. Change to EC on the meter and read EC in ms/cm.

    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.

    When reporting your PPM in a thread, please give the conversion factor your meter uses. For example: 550 PPM @0.7 or give the reading in EC, which should be the same meter to meter.

    It may also be advisable to give the starting value of your water; there is a huge difference between RO and distilled water with a PPM of approximately 0 and hard tap water of PPM 300 @.5 (notice the conversion factor so others can work out the EC) or well water with a conductance of 2.1 ms/cm.

    A note to Organic Growers:
    An EC meter has fewer applications for a soil grower because many organic nutrients are not electrically charged or are inert. Things like Superthrive or Fish Emulsion, blood meal, rock phosphate or green sand cannot be measured with a meter reliably when they are applied or in runoff. Meters can only measure electrically charged salts in solution.

    "The solution"...
    When reporting your PPM in a thread please give the conversion factor your meter uses for example 550 PPM @.7 or give the reading in EC (the EC should be the same meter to meter).


  13. #13
    Extreme Koi Member Rank = Supreme Champion Davej's Avatar
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    Quote Originally Posted by Dave Collins View Post
    How about this then:

    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 liter 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.

    Electrical Conductivity (EC) is expressed in siemens per centimeter (s/cm) or milliseimens per centimeter(ms/cm). It can be determined with an inexpensive hand held meter. Nutrient ions have an electrical charge, a whole number, usually a positive or negative 1, 2, or 3. EC is a measurement of all those charges in the solution that conduct electricity. The greater the quantity of nutrient ions in a solution, the more electricity that will be conducted by that solution. A material has a conductance of one siemens if one ampere of electric current can pass through it per volt of electric potential. It is the reciprocal of the ohm, the standard unit of electrical resistance. A siemens is also called a mho (ohm backwards).

    For convenience, EC measurements often are converted to TDS units (ppm) by the meter.

    The meter cannot directly measure TDS as described above, and instead uses a linear conversion factor to calculate it. Everyone’s nutrient mix is different, so no factor will be exact. The meter uses an approximate conversion factor, because the exact composition of the mix is not known. Conversion factors range from .50 to .72, *depending on the meter manufacturer, which do a good job of approximating a TDS calculation from the meter’s measurement of EC.

    * All ppm pens actually measure the value based on EC and then convert the EC value to display the ppm value, having different conversion factors between differing manufacturers is why we have this problem communicating nutrient measurments between one another.

    EC is measured in millisiemens per centimeter (ms/cm) or microsiemens per centimeter (us/cm).

    One millisiemen = 1000 microsiemens.

    EC and CF (Conductivity Factor) are easily converted between each other.
    1 ms/cm = 10 CF

    "The communication problem"...
    So again, the problem is that different ppm pen manufacturers use different conversion factors to calculate the ppm they display. All ppm (TDS, Total Dissolved Solids) pens actually measure in EC or CF and run a conversion program to display the reading in ppm's.

    There are three conversion factors which various manufacturers use for displaying ppm's...

    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.

    Place the probe in the solution and read TDS in ppm. Change to EC on the meter and read EC in ms/cm.

    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.

    When reporting your PPM in a thread, please give the conversion factor your meter uses. For example: 550 PPM @0.7 or give the reading in EC, which should be the same meter to meter.

    It may also be advisable to give the starting value of your water; there is a huge difference between RO and distilled water with a PPM of approximately 0 and hard tap water of PPM 300 @.5 (notice the conversion factor so others can work out the EC) or well water with a conductance of 2.1 ms/cm.

    A note to Organic Growers:
    An EC meter has fewer applications for a soil grower because many organic nutrients are not electrically charged or are inert. Things like Superthrive or Fish Emulsion, blood meal, rock phosphate or green sand cannot be measured with a meter reliably when they are applied or in runoff. Meters can only measure electrically charged salts in solution.

    "The solution"...
    When reporting your PPM in a thread please give the conversion factor your meter uses for example 550 PPM @.7 or give the reading in EC (the EC should be the same meter to meter).

    Dave

    Yes its certainly... interesting?

    Frequently Asked Questions - HM Digital is a good read.

    Agree EC rules So easy to forget that TDS in ppm is simply a representation calculated by men in white coats in a lab looking at the correlation between conductivity and the distilled solids that are left in their test tubes..

    You could take the pin a tail on the donkey approach knowing that the TDS figure is just representational and plump for a number... But for there to be some meaningful track back to EC it does seem that you need to calibrate the particular unit to the expressed ppm solution for the particular scale it uses… In which case there seem to be three possible answers to Stuart’s question. 904 is one, 693 another...

    What meter are you looking to calibrate Stuart?

    Dave

  14. #14
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    hanna ph tds/ec combo just dug out paper work says tds factor 0.7ppm = 1us/cm

  15. #15
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    probe is hi 7634 fixed in unit

  16. #16
    Extreme Koi Member Rank = Supreme Champion Davej's Avatar
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    Quote Originally Posted by sff View Post
    probe is hi 7634 fixed in unit
    Drop me a pm of your address and I'll stick a half dozen sachets of Hi70442 1500ppm in the post, they are redundant to me..

    Dave

 

 

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