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Old 11-22-2008, 03:33 PM
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Default Things Explained TDS and pH

TDS and pH Explained
We all know that plants, whether they are growing in a hydroponic system or a soil system, require nutrients. But choosing the right nutrient formula is just the first step. Maintaining the proper nutrient strength can have a substantial impact on plant performance; therefore any serious grower should have a TDS or EC meter available. Even after adjusting the strength of the nutrient solution to meet the plant’s needs, the nutrients still may not be available to the plant if the pH is not is not within the proper range. Thus, a pH meter is a vital piece of equipment that should be a part of every growers arsenal. In this month’s article we are going to take a closer look at TDS, pH, and the meters that are used to measure the nutrient solution.





What is TDS/PPM/EC



Firstly, TDS (or Total Dissolved Solids) is measured in units of PPM (or Parts Per Million). EC (or Electrical Conductivity) is measured in either µS (MicroSiemens) or mS (MilliSiemens). In the USA we use PPM and internationally µS and mS are the preferred measurements. Both TDS and EC meters measure nutrient strength in the same way with the same accuracy; however the readouts are displayed differently. For example: a nutrient solution that measures 1000ppm, on a TDS meter, will be the same strength as a solution that reads 1430 µS or 1.43 mS on an EC meter.

TDS and EC meters measure the strength of a nutrient solution by measuring the flow of electrical current between two metallic probes. The higher the salt concentration in the nutrient solution the better it conducts electricity; therefore the higher the reading on the meter. It is extremely important that the batteries are in good, strong condition and the probes must always be clean from salt deposits. Weak and dirty probes will effect the accuracy of the reading and are the biggest causes of inaccurate readings.





PPM Conversion Factors



Not all TDS meters will give the same PPM reading. The main reason for this is that different meters will use different conversion factors. These conversion factors are based off the EC reading. For example: A meter that uses a conversion factor of 0.5 will display a reading of 0.5 times that of the EC reading. If the EC reading is 1000 µS then the ppm reading will be 500 ppm. It is as simple as multiplying 1000 by the conversion factor of 0.5. If the meter uses a conversion factor of 0.7 (the most common conversion factor used) then 1000 µS would be 700 ppm (1000 x 0.7). When purchasing a TDS meter it is very important to find out what the correct conversion factor is for the meter. It could make a difference of more than 200 ppm! Not only is it important to know what the conversion factor for the meter is, it is also important to know the conversion factor of the calibration solution. Generally speaking, Genesis calibration solutions are for meters that use a 0.7 conversion factor and the Hanna solutions are for meters with a 0.5 conversion factor.



0.5 conversion 0.7 conversion Adjustable conversion
- Hanna Primo - Hanna HI 9813-0 - Hanna HI98129
- Tri-Meter - Hanna HI 9813-6 - Hanna HI98311
- Hanna HI981504 - Hanna HI 983301N - Hanna HI981404
- Hanna HI 983311
(no calibration required) - Hanna HI981404N
- Blue Lab Truncheon TDS/EC (displays reading in PPM (0.5 and 0.7) and ECM
- Oakton Meters

Click here to find out how to calibrate these meters.







pH Levels



pH meters measure the concentration of H+ (acids) and OH- (bases or alkali‘s). A pH of 7 has no free H+ or OH- ions. A pH of less than 7 has H+ ions and a pH of more than 7 has OH- ions. A pH value lower than 7 is considered acidic; a pH value higher than 7 is considered alkaline. A pH value of exactly 7 is considered neutral. The correct pH of a nutrient solution is vital for the uptake of nutrients by the plant roots. The following figure shows the availability of different minerals at varying pH levels. As you can see, most of the elements are at their highest availability at a pH of between approximately 5.5 and 6.0.










Click here to find out how to calibrate your pH meter.





Recommended PPM, EC and pH Values for Various Feeding Programs



Vegetative for Hydroponics

Growth Stage
0.5 Conversion (ppm)
0.7 Conversion (ppm)
EC ( µS)
pH

Clones/Seedlings
220-350
300-500
430-700
5.5-6.2

Week 1-2
400-550
600-800
850-1100
5.5-6.2

Week 3-4
550-700
800-1000
1100-1450
5.5-6.2

Flowering for Hydroponics

Week 1-2
700-850
1000-1200
1450-1700
5.5-6.2

Week 3-4
700-1000
1000-1400
1450-2000
5.5-6.2

Week 5-6
850-1000
1200-1400
1700-2000
5.5-6.2

Week 7-8
350-700
500-1000
700-1450
5.5-6.2







Vegetative for Soil

Growth Stage
0.5 Conversion (ppm)
0.7 Conversion (ppm)
EC ( µS)
pH

Clones/Seedlings
220-350
300-500
430-700
6.2-6.8

Week 1-2
400-550
600-800
850-1100
6.8-6.2

Week 3-4
550-700
800-1000
1100-1450
6.2-6.8

Flowering for Soil

Week 1-2
700-850
1000-1200
1450-1700
6.2-6.8

Week 3-4
700-1000
1000-1400
1450-2000
6.2-6.8

Week 5-6
850-1000
1200-1400
1700-2000
6.2-6.8

Week 7-8
350-700
500-1000
700-1450
6.2-6.8


Please note that most soil growers only feed every second watering to avoid salt buildup.





Differences in readings between two meters



Some growers will notice that their readings will sometimes fluctuate, especially when using two different meters in the same nutrient solution. There are a number of possible reasons for this. The two meters may use different brands of batteries. One set of batteries may be older than the other (the batteries may supply the same voltage, however, the power from older batteries is weaker). Even corrosion on batteries and/or battery contacts will cause differences in readings. Unseen dirt on probes can effect the readings from one meter to another. Probes need to be cleaned regularly to keep dirt and salt crystals from accumulating on the probes. One of the most important points a grower needs to understand about why two meters might display a slightly different reading from another is that these meters are hobby meters. Even though these meters may cost up to $250 these meters are still hobby meters and are cheap in relation to laboratory bench meters. Laboratory and commercial meters are priced from about $1000 and up and, in most cases, are overkill for a typical hydroponic garden. If two meters in the same solution have different readings of up to 100 ppm don’t worry about it, it’s not such a big difference. For pH meters, if the difference is 0.3 or less its not that significant.


Intellidose - Intelligent Dosing System



The new Intellidose system is perfect for those hydroponic growers that want to completely automate the monitoring and adjusting of their nutrient solution. This new dosing system is based on the popular commercial system that is used world wide for commercial farmers. The Intellidose is completely adjustable from either a PC or from the Intellidose unit directly. Every Intellidose system comes with a PC interface and software which allows the grower to have complete control over nutrient dosing and pH adjustment, EVEN remotely! The Intellidose will allow the grower to use a three part nutrient program and a pH up or down. If the a two part nutrient solution is used then the grower can utilize the third dosing tank for enhancers, e.g. PK 13/14 or Sweet etc. The grower can program the controller unit or use the PC software to set a weekly program for nutrient dosing. This will allow the grower to keep up with the crop’s nutrient requirements on a daily bases. The crop will be fed at peek rates continuously, thus allowing for maximum growth and production. The grower can also remotely activate a pump and drain the reservoir (advisable only if the reservoir can be filled with an auto shut-off kit). Once the reservoir is filled with fresh water the grower can initiate an irrigation cycle that will allow flushing of any salt build-up. Once the flush has been completed, the reservoir drained again and refilled the dosing system can be reactivated. Nutrients will be injected (according to growers set program) until required PPM level is attained and the pH will also be balanced. The Intellidose allows for all of this to be done remotely.


Once the grower has set the desired pH level, the Intellidose will keep the pH just below the set pH. If a desired pH level is 5.8 then set the pH on the Intellidose to 5.9 or 6. Every time the pH of the nutrient solution reaches the set level, pH Up or pH Down (the grower must choose either Up or Down for pH adjustment) will be will be injected into the solution. Rockwool growers will love this feature as the pH of their nutrient solution always creeps up over 7 over a 24 hour period; this will not happen with the Intellidose system.


One of the best features that this system offers the grower (if the system is connected to a PC) is data logging. The Intellidose will log data (EC, PPM, pH and water temperature) every 5 minutes and will display the data in a spreadsheet or as a graph. The graph is displayed for a 24 hour period, it also allows the user to scroll backwards in time to see data from previous days.



The IntelliDose has many other amazing features. If your a serious grower, after using one yourself you'll wonder how you ever got along without it.


This infomation was obtained from http://www.bghydro.com/

Last edited by Mrgreenjeans; 12-02-2008 at 04:11 AM.
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Old 11-22-2008, 08:46 PM
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All those "things explained" took some time to write out.Thanks for the good knowledge and time,for us beginners.
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Old 11-23-2008, 01:30 PM
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Quote:
Originally Posted by mr.anonymous
All those "things explained" took some time to write out.
Hey man,
I know you did a bunch of these threads, I've not read them all. I have checked out a few and couldn't see any indicator of credit given to the author or source. This particular post begins with a reference to "this month's article". Most of the information on this site and other sites is c/p from someone somewhere. It's ok to do that...would you please source it?

I do recognize the benefit of the information and the time/effort is took to post and for that I thank you.

peace

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Old 11-24-2008, 02:50 AM
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No worries at all Gratitude I will edit the posts and add where and from who I got them ...



Quote:
Originally Posted by Gratitude
Hey man,
I know you did a bunch of these threads, I've not read them all. I have checked out a few and couldn't see any indicator of credit given to the author or source. This particular post begins with a reference to "this month's article". Most of the information on this site and other sites is c/p from someone somewhere. It's ok to do that...would you please source it?

I do recognize the benefit of the information and the time/effort is took to post and for that I thank you.

peace

Grat
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Old 11-24-2008, 03:27 AM
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I noticed the PH guide you have posted is for Hydro settings, here is a link to a chart for hydro and soil settings. That way the dirt dogs like myself won't get confused and set the PH to low.

http://www.growkind.com/gallery/data..._and_hydro.JPG
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Old 11-24-2008, 04:27 AM
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Heres the link you posted weed sprite


Quote:
Originally Posted by weed sprite
I noticed the PH guide you have posted is for Hydro settings, here is a link to a chart for hydro and soil settings. That way the dirt dogs like myself won't get confused and set the PH to low.

http://www.growkind.com/gallery/data..._and_hydro.JPG
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