µS?

[SunLake]

What is this measuring? µS

OK I understand its conductivity. And it can be used for calibration I assume... but do I really need this for anything besides that?

SunLake Reviewed by SunLake on 10-29-2009. µS? What is this measuring? µS OK I understand its conductivity. And it can be used for calibration I assume... but do I really need this for anything besides that? Rating: 5

[DreadedHermie]

Showoff. I have no "mu" symbol on my Walmart keyboard.

Thassa micro-siemen. It is a measure of conductivity. Siemens are the reciprocals of ohms. They are also what make my pants crunchy. :thumbsup:

Electrical conductivity (EC) is what a "TDS meter" is actually reading.

Your "ppm" is then estimated using a conversion factor of your meter manufacturer's choosing. So, while a ppm reading may vary according to the conversion algorithm, EC is "constant."

International discussions are often in EC terms to avoid the skewing caused by different conversion factors.

Don't know if you need it or not. But if you're not gonna use that "mu" character...

[Horsemanrocks]

This may helpâ?¦.or not, but if you want to track your ppmâ?¦.you gotta learn it sometime.

If you really want to succeed, then understanding ppm will become important at some point. A good example would be that if you were having problems, and posted in the problems sections, â??those that helpâ?� wouldnâ??t be able to assist you without your supplying ppm. And in the long run youâ??ll have to understand it yourself to have success. Time to â??bite the bulletâ?�.

It will become more understandable in timeâ?¦.take the ppm of your tap waterâ?¦. add nutrients and check thatâ?¦.try some RO or distilled water and check thatâ?¦and read.

Copied and pastedâ?¦.not my work.

Main Menu

pH / EC / TDS / PPM
How do I tell if my PPM/EC is too high or too low?
It's simple to find out if you are using too much food or not enough by watching the nutrient concentration levels in your tanks day to day. Don't be concerned with the exact reading, rather watch how it rises and falls from each day to the next. The differences between when you put the solution into the tank and the readings you get several hours later or the next day are what tell you if your plant is eating, drinking or happy.

Start with 1.00 EC (or a SAFE nutrient strength). Next day, if it reads 1.4, it means your plants have been using water and your nutrient solution is becoming more concentrated. This means the concentration of nutrients is too high, so you dilute.

If the meter reads lower than the previous day, 0.7 say, it tells you that the plants are eating nutrients faster than they are drinking water, so you should increase your nutrient strength. If it remains the same, your feeding schedule is on target for now. The nutrient/water intake fluctuates with the growth of the plant, so you must continually monitor it day to day.

Your plants will tell you the optimum nutrient levels. When they are receiving optimum food and water, the readings remain constant. The more you do it, the easier it gets. The reason no one can tell you what PPM/EC levels to use is because every garden is different and every plant has different requirements due to their particular environment. That's why you have a ball park starting figure, but after that your plants will tell you almost exactly what they require


Main Menu

pH / EC / TDS / PPM
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. Everyoneâ??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 meterâ??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 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




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Siemens are the reciprocals of ohms. They are also what make my pants crunchy.
Hermieâ?¦.In retrospectâ?¦.you are the â??perfectâ?� klingerâ?¦.apologies. HMR

Good luck SL
HMR

[doyoulikegreen]

Question:

Ok, so now I've started reading in EC instead of PPM (Thank You!). But when I am tending, what should I measure and adjust first PH or EC?

Thanks