can some body explain ppm to me please?

full of purple

full of purple

Well-Known Member
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
 
ScoobyDoobyDoo

ScoobyDoobyDoo

Well-Known Member
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.
 
greenthumb111

greenthumb111

Well-Known Member
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
 
Grojak

Grojak

Well-Known Member
are you planning to start watering based on PPM? I made the switch to doing it a few months ago..
 
ru4r34l

ru4r34l

Well-Known Member
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.

http://www.420magazine.com/forums/how-grow-marijuana/71813-what-difference-between-ppm-ec.html said:
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).
Click to expand...
regards,
 
Grojak

Grojak

Well-Known Member
If you buy an EC meter great, but if you're going to be converting everything to PPM why not just buy a PPM meter? When you are ready to do so ask some more specific questions (and do some research of your own please) regarding PPM/EC usage... For instance what I do is 200ppm in my clone machine... this is about 1tsp cloneX per gal and 3 drops super thrive.

400-600 in veg and 600-800 in flower, am I right, am i wrong? Ask the plants they will tell you everything, you'll also probably find out you don't change you feeding much. For me I use Fox Farm Tiger Bloom and Big Bloom and Gen Organics Grow and Gen ORganics Bio Weed

veg is 3tbs Big Bloom, 3tsp Grow and 1/2 tsp BioWeed(seaweed extract)

flower im not certain on yet, have not flowered since I started doing this, but will begin playing with it next watering :)
 
1

1hit

Member
I am 1 week into my first grow and am wondering how often to give my seedlings nutrients. They seem to be doing well and I have just started feeding with 100ppm in distilled water. I have them in 1 inch rock wool and water once a day. Is adding nutes every other watering adequate? Also, do I need to add secondary nutrients in addition to NPK?
 
obijohn

obijohn

Well-Known Member
Ok, I'm confused. So ppm is what some folks use to measure how much nutes to feed? If that is correct, I'd think it wouldn't be accurate. Some nutes will let you use tablespoons per gallon, some will burn your plants with a teaspoon. Ppm wouldn't measure the strength of the nutes, just the amount then, right?

Seems that just using the recommended dosage or less would be the better, and easier way to go.

...or maybe I just misunderstand what it is
 
K

Kervork

Well-Known Member
What I do is mix according to manufacturer instructions, or in some case 50 -75% of recommended. Then I take a reading. Say for example I get 1000 ppm. after mixing everything. Later after plants use nutrient and suck up water I see that my PPM are down to 700, I will add water and nutrients. If I see that my PPM's are up to 1200, that means water is evaporating more than nutrients are being used and I will add just straight water to dilute the nutrients. Comparing current PPM to what I had when I started gives me an indication of what I need to use to get things back to normal.

Meters are useful when you recirculate and don't want to continually dump your rez and remix.
 
D

drewbot

Member
obijohn said:
Ok, I'm confused. So ppm is what some folks use to measure how much nutes to feed? If that is correct, I'd think it wouldn't be accurate. Some nutes will let you use tablespoons per gallon, some will burn your plants with a teaspoon. Ppm wouldn't measure the strength of the nutes, just the amount then, right?

Seems that just using the recommended dosage or less would be the better, and easier way to go.

...or maybe I just misunderstand what it is
Click to expand...
Well I'm a chem professor so I can give you a whole lot of jargon but the simple answer to that specific question is

(1) Some molecules are heavier than others, so Barium Sulfate will be about 5 times heavier than Magnesium Chloride (5 tablespoons of Barium Sulfate has the same number of "transition metal" molecules as 1 tablespoon of Magnesium Chloride)

(2) Some solid media are built up with inert soluble salts (uncommon)

(3) Some media is active at much lower values, and are toxic at high values (Silver)

(4) Some media is WAY active at insanely low values, usually PGR's. 0.5 micromols per liter for many PGR's.

When you say "strength" and "amount" I don't know exactly what you are refering to. PPM measures how much dissolved solid is in there. For an "ideal solution" - -which is an aqueous mixture at near room temperature -- 1 PPM is 1 mg of solute dissolved in 1 L water (solvent). So 1000ppm means that when you water 1 liter onto your plants you're also giving them 1 gram of solid stuff. If you put that liter on a hotplate and boil it off you should be able to scrape off the better part of 1 gram. Now it also considers H+ and OH- ions but it doesn't really add up to much around pH 6 which is exactly 1 part H+ per million parts H20.
 
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