PPM?

[ferd]

i don't understand what every one is talking about when descussing ppm's

[fishman3811]

PPMs is parts per million meaning how much food is in your medium or res.

[postmandave]

this may help u understand ppm is parts per million and is one way to measure the strenth of nutrient solutoin that you are feeding the plants with , it can also be done wth ec meter and tds meter have a read courtesy of mariauna matt.


ELECTROCONDUCTIVITY, PARTS PER MILLION, TOTAL DISSOLVED SOLIDS

There are various methods of measuring the concentration of nutrient solutions. In the past growers measured the main nutrients individually whereas the current trend is to measure a substance that reflects total nutrient levels. Measurement devices commonly used for this include Electroconductivity (EC) meters, CF meters, Parts per million (PPM,TDS) meters, and/or a combination of these. None of these methods provides an exact analysis of total nutrient levels; all are an estimation, and are based on conductivity readings.

Note: Conductivity is based on scientific material. Scientific material can be painstaking to read, but the way to read it is to read a segment until it is understood before going on to the next segment. If material discussed includes material one has forgotten, it is advisable to go back and review it.

Electroconductivity
Conductivity is expressed in metric units. Because electroconductivity (EC) meters read out in metric units, one needs to understand the units and how to convert back and forth between them. The Systeme Internationale (SI) is the international standard for the metric system. An example is the SI unit for length, which is the meter (m). Scientific calculations/formulations etc., are based on the meter or derivative of the meter (centimeter, millimeter, etc.). SI terms and units relevant to electroconductivity are:

Resistance: Electrical resistance is the ability of a material to oppose the flow of an electric current. The SI unit of resistance is the Ohm, named after the German physicist Georg Simon Ohm (1789-1854). Its symbol is the capital Greek letter omega or â??Ώâ?�.

Conductivity
Conductivity is the reciprocal of resistivity. Hydroponic electrical conductivity measures the rate at which a small electrical current flows through a solution. The SI unit of conductivity of an element with a resistance of 1 ohm is the Siemens, named after German physicist Ernst Werner von Siemens. The unit was originally called Mho (reverse spelling of Ohm), but has been replaced by Siemens. Although some hydroponic growers use the older term Mho, the SI unit Ohm will be used in this discussion. Also, although some hydroponists refer to conductivity in Siemens (S), the unit of conductivity is actually S/ centimeter (cm). (Note: 1 cm = 1/100 meter (m).

Hydroponic electroconductivity is measures in milliSiemens/cm (mS/cm) or microSiemens/cm (µS/cm). The prefix micro stands for 1/1,000,000. Importantly, the micro symbol is not â??u,â?� but Mu (µ); a u with a long leg in front of it. Mu is the twelfth letter of the Greek alphabet. Mu may be written as a u on some html material because it was not coded in html language coded for Mu.

Importantly, the abbreviations for microSeimens and miliSiemens can be written in a similar manner. For example, microSiemens per centimeter can be abbreviated m S/cm and milliSiemens per centimeter can be abbreviated mS/cm. The difference between the two is a space or no space between the m and S. These are different measurements since mili = 1/1000 and micro = 1/1,000,000. These abbreviations are easy to mix up, and for the purposes of this writing, the abbreviation for micro will be Mu (µ).

Although Conductivity Factor (CF) is not a recognized scientific measurement, CF meters are used to measure electroconductivity in CF units. These are scaled from 0 to 100, where 0 represents pure water. The conversion of CF to Siemens is 1mS/cm = 10 CF. (Note: Even pure water conducts electricity. Even if all electrolytes are removed, conductivity is not zero. This is because a very small part of the molecules of water are ionized as hydrogen ions and hydroxide ions. Pure water has a conductivity of < 1 µS/cm).

Conductivity and electrolyte strength
Conductivity readings are based on the strength of electrolyte being measured. An electrolyte is a solute that dissociates (splits apart) fully or partially into ions when dissolved in a solvent, producing a solution that conducts electricity. A solvent is the most abundant substance in a solution. A solute is a substance which is dissolved in a solvent to make a solution. For example, when salt is dissolved in water, water is normally the solvent and salts are the solute. There are three strengths of electrolytes:

1. A strong electrolyte is a solute that completely dissociates into ions in solution. Solutions of strong electrolytes conduct electricity. For example, sodium chloride (NaCl) is a strong electrolyte and good conductor because it completely ionized to Na+ and Cl-. The greater the amount of Na+ and Cl- contained in water the more electricity is carried, and the higher the conductivity. Strong acids such as nitric acid (HNO3), and strong bases are also good conducting solutions. Calibrating solutions, EC, and thus PPM readings are based on the conductivity of strong electrolytes.

2. A weak electrolyte is a solute that incompletely dissociates into ions in solution. Since there is less ionization, most of the molecule stays together. The resulting solution contains both molecules and ions. Insoluble salts, and weak acids (i.e., vinegar) or weak bases form poorly conducting solutions. A solution of a weak electrolyte can conduct electricity, but usually not as well as a strong electrolyte because there are fewer ions to carry the charge from one electrode to the other.

3. Non-electrolytes do not dissociate much at all. An example is sugar water.

An EC meter applies a weak electrical voltage to the solution across a pair of electrodes and reads the current that is produced from the electrolytes. EC is a measure of the total ion content of the nutrient. Since salt is a strong electrolyte, the higher the salt content, the greater the flow of electrical current. Double the strength of the solution does not double the conductivity, however due to interaction between the salts in solution. Salts have a saturation point in which the ions act against each other, making it hard for electricity to flow.

Nutrient solutions contain various strengths of electrolytes and only ionized electrolytes are read by meters. This means that substances that are weak or non-electrolytes such as nitrogen or phosphorous containing compounds may not be read by the meters. Thus, electrical conductivity does not give any indication of which nutrient ions are present, nor information about undissolved nutrients; it is an estimation of the overall available nutrient levels. Too high an EC results in vegetative growth with little fruit or flower production and too low an EC produces weak, unproductive plants.

PARTS PER MILLION (PPM), TOTAL DISSOLVED SOLIDS (TDS)

Ppm refers to concentration expressed as parts of solute per million parts of solution. This normally refers to parts per million by mass. (Note: Mass = weight divided by 9.8 meters/second squared on planet earth). In very dilute solutions, ppm is approximately equal to milligram (mg) solute per liter of solution. PPM meters take an EC reading and uses a conversion factor to convert the results to total dissolved solids (TDS) which reads out in parts per million (PPM). Since TDS are ionic compounds, An EC reading is the basis of PPM meters.

Hydroponic ppm is measured in µS/cm. While there is no direct relationship between µS and ppm for mixtures, a conversion factor is used to estimate TDS. Meters may have built in or user adjustable conversion factors. Controversy arises, however, because different manufacturers may use different conversion factors, and it is possible to get different readings from the same calibrating solution. To avoid this, a conversion factor of 0.64 to calibrate meters is recommended. A user adjustable feature on the meter allows one to change the conversion factor.

Some sources refer to ppm readings being inaccurate. PPM is used widely in science, but it is used to measure specific substances. In hydroponics, it is used to measure a specific substance (s), with the intent of reflecting an estimate of total nutrient levels. Neither EC or ppm readings are exact; both are estimates. The only way to get an exact measurement of a nutrient is to measure that nutrient individually (i.e., ion chromatography) which is beyond the scope and/or necessity of most hydroponists. Importantly, an understanding of PPM is necessary if one intends to mix their nutrient solutions.

CALIBRATION SOLUTIONS
Standardized calibrating solutions are used to calibrate a PPM or EC meter. These are strong electrolytes, which would conduct the most electricity. The bottles are marked with the conductivity (EC) value in µS/cm and the corresponding ppM values. Three examples of calibrating solutions are:
4. Sodium chloride (NaCl): A 1000 ppm NaCl standard is most frequently used when calibrating the meter for hydroponic solutions.
5. Potassium chloride (KCL): Standard values used in hydroponics are 2760 µS/cm or 1413 µS/cm at 25 degrees C.
6. "442" mixture: The 442 standards are made from Sodium Sulfate (40%), Sodium Bicarbonate (40%) and Sodium Chloride (20%); thus 4-4-2.

Calibration tips and/or errors in calibration:
â?¢ Keep daily logs.
â?¢ Calibrate routinely, using fresh, properly stored calibration solution each time. Do not return the solution used for calibration to the original container as it will contaminate it.
â?¢ Old nutrient should not be used since it may have concentrated salts and result in inaccurate readings.
â?¢ Calibration measurements should be performed with consistent solution temperatures. Furthermore, the calibration solution temperature should be as close as possible to the nutrient solution. One should also wait the time recommended by the manufacturer so the electrode can come to the same temperature as the nutrient temperature. A temperature compensation table, usually supplied with calibration solutions gives recommendations for calibrating meters at different temperatures.
â?¢ Probes should be dry prior to calibration. They should be rinsed or cleaned with the factory recommended solution/method after using them. If they are not rinsed thoroughly after each reading they will eventually get a build up of dirt and scale on them which can cause inaccurate readings. Meters should be stored in a cool, dry place. Also, one should not insert a stick electrode above its waterproof level since the electrode can be damaged. Electrodes can be expensive, so proper care can save money.
â?¢ Hard water can contribute to a high EC level. Calcium (Ca) and other substances can contribute to the hard water; thus hard water is usually expressed as ppm Calcium carbonate (CaCO3). Water with hardness over 80 ppm CaCO3 is often treated with water softeners. Tap water with a TDS level > 200 pm is considered hard water. If hard water is suspected, an analysis listing, available from the water company should be obtained. This usually includes the TDS, as well as pH, and mineral levels, for the tap water in oneâ??s area.

Methods of dealing with hard water includes water filters, reverse-osmosis units, distillers, and de-ionizers. One can determine whether a filter or other method is working properly by measuring the conductivity before and after the filtration.

METER SELECTION
Tips on meter selection include:
â?¢ Desirable characteristics include water proof, auto shut off, and adjustable conversion factor.
â?¢ Accuracy: Accuracy of meters is specified in terms such as accuracy of specific measurements (TDS, temperature, EC) and resolution.
â?¢ Set point: This allows one to set a parameter in which an alarm is activated if the solution goes outside of the parameter(s).
â?¢ Beta: Some meters have an adjustable temperature coefficient factor (Beta or Ã?). Beta is a temperature coefficient that can be adjusted for some lab situations (i.e., electronics, chemistry labs) but is not needed for hydoponics. Use of the Beta factor requires calculus skills and is beyond the scope of the FAQ.
â?¢ TDS and EC range: meter selection may be based on the plants grown and their recommended readings. One should investigate the EC and TDS range they need to measure on the particular crop they are growing. One may not need a high range and possibly more expensive meter if the crop they are growing has a low recommended EC or TDS. For example, the ppm of a bromeliad is low (560-840 ppm); and if one were raising only bromeliads a meter with a capacity of 3000 ppm would be unnecessary.
� Temperature compensation feature: The ppm conversion factor is affected the temperature of the solution. If the temperature deviates from 25 degrees C, then the meter compensates for the difference. When the solution temperature is measured, the value for conductivity obtained at that temperature is converted to a value for conductivity as if the temperature were 25 °C. (Note: Temperature is based on the Centigrade (C) measurement. For those familiar with Fahrenheit, the conversion is C = (F-32)X(5/9). Some meters provide readouts in C and F.
â?¢ Temperature range: Temperature ranges for the meter are given in degrees C, so conversion is necessary if one is used to the Fahrenheit system. Very high temperature ranges or extremes may not be needed in temperate climates, but are necessary for in desert or extreme areas.
â?¢ Electrode or probes may not be included with a meter and may need to be purchased separately. Probe warranties may be shorter than meter warranties, and the cost of replacement probes should be investigated. Longer probes may be needed to reach the nutrient depending on the hydroponic setup.
â?¢ Warranty: Different meters have different warranties. Less expensive meters may have shorter warranties, and probe warranties may be shorter than meter warranties.
â?¢ Alternative/add on features: Specialized computer software and other devices such as Analog-to-Digital converters are used by some growers. These devices can connect to pumps add nutrient as needed based on EC values.

Home made meters

Home made conductivity meters, made by using home made electrodes and taking the inverse reading of an ohmmeter reading are inaccurate. One reason is because of the method in which EC is measured. Electrolytic conductivity can be measured by either the alternating bipolar method or the electromagnetic induction method. Both methods involve applying alternating current (AC) voltage across the poles or coils. An ohmmeter applies direct current (DC), and thus does not meet the requirement for measurement. Furthermore, when an ohmmeter is placed in a nutrient solution, the hydrogen ion buildup on the negative terminal will act as a resistance and cause a false reading

[Scarlet Sky]

good job dave! now i don't have to do anything :D

[postmandave]

lol TY:D

[ferd]

do i need to worry about ppms if i didn't go the hydroponic route?

[herbaltivo]

Nope.

[ferd]

use fox farm for soil. figure every time repot...it would give plants nutes for another thirty days. was thinking feed 30 days after transplant, BETTER-GROW orchid bloom booster. 11-35-15. any ogjections?