can some body explain ppm to me please?

Never messed with my ppm or a ph meter but it means parts per million i think.
When ever i fertilize i just throw a pinch of what ever im ising in a gallon milk jug
let it sit for a couple hours shake up after and water my plants

part per million is used to measure the amount of dissolved solids in your nutrient solution. the more mature a plant is the higher the ppm of your solution should be. usually you start around 150ppm for seedling/clones and move all the way up to as high as 1800ppm for late flower plants.

PPM = Parts per million and EC = Electrical conductivity
Both ofthese are measurements of solutes (things that can dissolve) in water. Partsper million is a mass measurement and in water quality it refers to a quantityof a ion or compound in water, like nitrate (100 ppm of nitrate in your watersample). Most of the fertilizers have what are referred to as salts likenitrate salts, phosphate salts. If you measure the water before you addanything to it, you will get some ppms unless you are using deionized water. Thisis because there are dissolved ions of calcium, magnesium, etc. in the waterthat have dissolved from the ground or your pipes (metals). My water is highwith around 300 ppm and some can be as high as 600 ppm depending on where theyget their water. RO water usually is below 50 ppm because a lot of the saltsand ions are removed through filtration. Deionized has all the ions removed andshould be 0 ppm. So if you have a water that is 200 ppm to start and you addyour fertilizer and your water is now 400 ppm, you have just increased thedissolved compounds/ions of your water.


EC on the other hand, if not measured directly, can be derived by dividing thePPM by 500 or 700 to arrive at the correct EC. EC is measured in Micro Seconds.Most meters in the US are 700 as our PPM numbers are usually given based uponthat conversion factor. Pure water is not conductive, but as you add salts tothe water it becomes more conductive. So as you add more fertilizer, your ECincreases.


Hope this helps

GT

Originally Posted by greenthumb111

EC is measured in Micro Seconds

Sorry for being picky.
Electrical conductivity is measured in siemens per centimeter (S). In hydroponics you will most often see EC expressed in millisiemens per centimeter (mS).

thamks guys

are you planning to start watering based on PPM? I made the switch to doing it a few months ago..

yh i am

Here is a post I have read many times, especially when buying and calibrating a new unit. I have given up my membership at this forum but was there for +3 years. It is not a new post but essentially has all the info you need.

Originally Posted by http://www.420magazine.com/forums/how-grow-marijuana/71813-what-difference-between-ppm-ec.html

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 shoul d be the same meter to meter).

regards,