TDS .5 vs .7 conversion factor?

Tahmi.Guhnn

Active Member
One last time.

You have a resevoir of nutrients that measure 1.0 EC

There are 3 scientists standing in front of you and each has a different meter.

You ask scientist number 1 what the PPM conversion is from his meter and he says that at EC of 1.0 there are 500 PPM of electrically conductive particles in the water.

You ask scientist number 2 what the PPM conversion is from his meter and he says that at EC of 1.0 there are 640 PPM of electrically conductive particles in the water.

You ask scientist number 3 what the PPM conversion from his meter and he says that at EC of 1.0 there are 700 PPM of electrically conductive particles in the water.

PPM = Parts Per Million. There can only be one correct answer for the number of electrically conductive particles in the solution.

And ultimately your answer is that it is because of the conversion factor the company uses... All 3 answers cannot be correct if we are truly talking about parts per million.
dude i didn't make the conversion factors. i didn't put the system into play. IT IS WHAT IT IS. and there isn't so many PPM of electically conductive particles in the water. an EC of 1.0 on a meter with a conversion factor of .5 show an ESTIMATE of 500 part per million. it is an estimate based on the EC. like i said before it doesn't count the particles. its a digital PPM reader. its not the old fashion way of finding the PPM so its really just an estimate. I dont know why but thats the way it is. if you want and exact PPM do this

Finding PPM of an Existing Solution

Find the volume of the solution. For example, if you were trying to determine the concentration of salt in water, determine how much water is in your container.

Remove the substance you are taking the concentration of from the solvent. The process will depend on the substance. For example, if you are trying to measure the concentration of salt in salt water, boil the water until only the salt remains.

Find the mass of the solute in milligrams. In this example, measure the mass of the salt crystals that are left.

Divide the mass of the solute in milligrams by the mass of the solvent in kilograms. For example, if you started with 2liters of water and were left with 3 milligrams of salt, you would convert the volume of water to mass. Because the mass of 1 liter of water is 1 kilogram, your total mass would be 2 kilograms. Then divide 3 milligrams by 2 kilograms to get 1.5 parts per million.

seriously dude come on. how can you not get this? like i thought you were fucking with me man about not getting it.
 

NLXSK1

Well-Known Member
Yeah, I basically said that PPM was unreliable and the important thing was EC and PH back in post 11 before you started jumping my shit...

Now that we have agreed that PPM is some estimate and the range is so wildly disparate that EC 1.0 might mean 500 ppm or it might mean 700 ppm and additionally somehow it depends on the manufacturer of the meter so essentially it is meaningless.

So thank you for completely missing the point of the situation and calling me an idiot while essentially agreeing with me...

I am gonna guess you are stoned... Probably not a great stretch there...
 

Tahmi.Guhnn

Active Member
Yeah, I basically said that PPM was unreliable and the important thing was EC and PH back in post 11 before you started jumping my shit...

Now that we have agreed that PPM is some estimate and the range is so wildly disparate that EC 1.0 might mean 500 ppm or it might mean 700 ppm and additionally somehow it depends on the manufacturer of the meter so essentially it is meaningless.

So thank you for completely missing the point of the situation and calling me an idiot while essentially agreeing with me...

I am gonna guess you are stoned... Probably not a great stretch there...
maybe you missed this post where i told him that PPM was a pain in the ass and he should just go with an EC meter.....

tds is not what you want to check there are about 3 or 4 conversion factors for tds. it converts from EC which is standard. i dont know the differences between the conversions it seems like a pain in the ass compared to just getting and EC meter.
I am going to guess you are stoned... wait no im not im gonna stick with the tard theory...
 

Brick Top

New Member
Some of the same info but maybe in a way that might help explain things ... maybe.

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 measurements 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 conversion 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 shoul d be the same meter to meter).


EC Hanna Eutech Truncheon CF
ms/cm 0.5 ppm 0.64 ppm 0.70 ppm 0
0.1 50 ppm 64 ppm 70 ppm 1
0.2 100 ppm 128 ppm 140 ppm 2
0.3 150 ppm 192 ppm 210 ppm 3
0.4 200 ppm 256 ppm 280 ppm 4
0.5 250 ppm 320 ppm 350 ppm 5
0.6 300 ppm 384 ppm 420 ppm 6
0.7 350 ppm 448 ppm 490 ppm 7
0.8 400 ppm 512 ppm 560 ppm 8
0.9 450 ppm 576 ppm 630 ppm 9
1.0 500 ppm 640 ppm 700 ppm 10
1.1 550 ppm 704 ppm 770 ppm 11
1.2 600 ppm 768 ppm 840 ppm 12
1.3 650 ppm 832 ppm 910 ppm 13
1.4 700 ppm 896 ppm 980 ppm 14
1.5 750 ppm 960 ppm 1050 ppm 15
1.6 800 ppm 1024 ppm 1120 ppm 16
1.7 850 ppm 1088 ppm 1190 ppm 17
1.8 900 ppm 1152 ppm 1260 ppm 18
1.9 950 ppm 1216 ppm 1330 ppm 19
2.0 1000 ppm 1280 ppm 1400 ppm 20
2.1 1050 ppm 1334 ppm 1470 ppm 21
2.2 1100 ppm 1408 ppm 1540 ppm 22
2.3 1150 ppm 1472 ppm 1610 ppm 23
2.4 1200 ppm 1536 ppm 1680 ppm 24
2.5 1250 ppm 1600 ppm 1750 ppm 25
2.6 1300 ppm 1664 ppm 1820 ppm 26
2.7 1350 ppm 1728 ppm 1890 ppm 27
2.8 1400 ppm 1792 ppm 1960 ppm 28
2.9 1450 ppm 1856 ppm 2030 ppm 29
3.0 1500 ppm 1920 ppm 2100 ppm 30
3.1 1550 ppm 1984 ppm 2170 ppm 31
3.2 1600 ppm 2048 ppm 2240 ppm 32​
 

FootClan

Well-Known Member
Some of the same info but maybe in a way that might help explain things ... maybe.

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 measurements 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 conversion 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 shoul d be the same meter to meter).


EC Hanna Eutech Truncheon CF
ms/cm 0.5 ppm 0.64 ppm 0.70 ppm 0
0.1 50 ppm 64 ppm 70 ppm 1
0.2 100 ppm 128 ppm 140 ppm 2
0.3 150 ppm 192 ppm 210 ppm 3
0.4 200 ppm 256 ppm 280 ppm 4
0.5 250 ppm 320 ppm 350 ppm 5
0.6 300 ppm 384 ppm 420 ppm 6
0.7 350 ppm 448 ppm 490 ppm 7
0.8 400 ppm 512 ppm 560 ppm 8
0.9 450 ppm 576 ppm 630 ppm 9
1.0 500 ppm 640 ppm 700 ppm 10
1.1 550 ppm 704 ppm 770 ppm 11
1.2 600 ppm 768 ppm 840 ppm 12
1.3 650 ppm 832 ppm 910 ppm 13
1.4 700 ppm 896 ppm 980 ppm 14
1.5 750 ppm 960 ppm 1050 ppm 15
1.6 800 ppm 1024 ppm 1120 ppm 16
1.7 850 ppm 1088 ppm 1190 ppm 17
1.8 900 ppm 1152 ppm 1260 ppm 18
1.9 950 ppm 1216 ppm 1330 ppm 19
2.0 1000 ppm 1280 ppm 1400 ppm 20
2.1 1050 ppm 1334 ppm 1470 ppm 21
2.2 1100 ppm 1408 ppm 1540 ppm 22
2.3 1150 ppm 1472 ppm 1610 ppm 23
2.4 1200 ppm 1536 ppm 1680 ppm 24
2.5 1250 ppm 1600 ppm 1750 ppm 25
2.6 1300 ppm 1664 ppm 1820 ppm 26
2.7 1350 ppm 1728 ppm 1890 ppm 27
2.8 1400 ppm 1792 ppm 1960 ppm 28
2.9 1450 ppm 1856 ppm 2030 ppm 29
3.0 1500 ppm 1920 ppm 2100 ppm 30
3.1 1550 ppm 1984 ppm 2170 ppm 31
3.2 1600 ppm 2048 ppm 2240 ppm 32​

thanks for the info....I did give all that info i said my tap water is 200ppm and my meter as a conversion factor of .5 and my nute reading after mixed was 1130ppm
 

NLXSK1

Well-Known Member
Thanks Bricktop. This paraprhased quote from your post might sum it up perfectly.

"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 shoul d be the same meter to meter).
* 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 measurements between one another.
Since almost nobody provides the conversion factor you should rely on EC since it is the same meter to meter.
 

Total Head

Well-Known Member
this thread just made my brain bleed. i haven't even smoked yet. i'm going to read through a few more times. apparently it needed to be discussed though. i had no idea.
 

homebrewer

Well-Known Member
this thread just made my brain bleed. i haven't even smoked yet. i'm going to read through a few more times. apparently it needed to be discussed though. i had no idea.
It's actually a very easy concept. I'm surprised this thread went further than post #6.
 

FootClan

Well-Known Member
Thanks Bricktop. This paraprhased quote from your post might sum it up perfectly.





Since almost nobody provides the conversion factor you should rely on EC since it is the same meter to meter.

Ok so what everyone is saying is if i want to find out how strong or weak my nute solution is i need to use an EC meter? correct?lol then why do we all use PPM meters?? if a ppm meter is just an EC meter converting what we see to a ppm measurement why dont we all just use ec..............why do we want to see the reading in PPM if PPM is not accurate?? im just trying to understand this once and for all and seems like more i learn about this subject the more question i have..........

if you say its so easy to understand homebrewer then why not jump in and make us all understand it better?? Is there any questions that arent considered to easy fo this forum??? just wondering how hard the questions have to be before they are considered valid questions......
 

Brick Top

New Member
Possibly just more regurgitation but maybe it will help make things a bit clearer. Maybe


When measuring a hydroponics solution in TDS it is recommended that the conversion formula TDS in ppm X .70 ( 442
Factor ) in stead of the usual .5 for aqueous solutions to obtain the equivalent EC reading.

To convert from uS/cm to mS/cm you divide by 1000

Example: 1,000 uS/cm = 1.00 mS/cm

EC meter display in uS/cm to convert to TDS -- If your TDS meter is calibrated using 1382 ppm or 6.44 ppt then
the conversion is (uS/cm x .50 factor) = (TDS) ppm

EC meter display in uS/cm to convert to TDS -- If your TDS meter is calibrated using 1500 ppm then the conversion
is ( uS/cm x .70 factor) = (TDS) ppm

Other examples:
2.00 mS/cm = 2000 uS/cm = 1000 ppm on .50 factor scale
2.00 mS/cm = 2000 uS/cm = 1400 ppm on the 442 scale or .70 factor scale
 

NLXSK1

Well-Known Member
It's actually a very easy concept. I'm surprised this thread went further than post #6.
The reason it blew up is because yes, it is a very easy concept (if you have the conversion factor) to calculate them back and forth. But obviously the same solution cannot be 500ppm and 700ppm at the same time. Therefore it is just a guess.

More importantly, how many people include the conversion factor when talking about PPM? I am gonna say about 5% or less. My basic point is, was and has been that discussing things in PPM is pointless because as seen above it is just a guess anyway.

I definitely can see how someone can have perfectly healthy plants at one PPM and another person have the same setup at the same PPM (with a different meter) and be having problems. We need to boycott PPM's.
 

NLXSK1

Well-Known Member
Because we care about PPM but cannot measure it directly and must use EC to generate an approximation of the PPM. So meters that measure EC are mostly if not all called PPM meters.
 

FootClan

Well-Known Member
Because we care about PPM but cannot measure it directly and must use EC to generate an approximation of the PPM. So meters that measure EC are mostly if not all called PPM meters.
Ok so i will buy a EC meter test my solution in EC and then use the chart to see what my PPM is? and this will give me a more accurate reading then using a ppm meter correct??
 

homebrewer

Well-Known Member
But obviously the same solution cannot be 500ppm and 700ppm at the same time. Therefore it is just a guess.
500 and 700 can be the same thing if they're on different scales just like uno and eins and one all mean the same thing. It doesn't matter what value or word you associate with the reading, it all has an EC equivalent.
 

NLXSK1

Well-Known Member
Ok so i will buy a EC meter test my solution in EC and then use the chart to see what my PPM is? and this will give me a more accurate reading then using a ppm meter correct??
Do you have your nutes nearby?

What do the directions on the back say?
 

FootClan

Well-Known Member
Do you have your nutes nearby?

What do the directions on the back say?
i use House and garden they just provide you with a nute chart and when i called humbolt wholesale they didnt really care or understand what i as asking and then just told me to follow the chart with 0ppm R/o water and everything will be fine.......they wouldnt tell me what my ppm should be at week 4 or 5 or anyweek just says to followthe nute chart which is ml per gallon
 
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