I am currently working on hydroponics systems. I need an EC meter with an output where i can connect it to my Arduino uno to get the readings. I have been searching for a device for quite along time but i cldnt find any1.. So any of u guys know a device which i can use? or any solution to this problem? pls be kind enough to reply back either here or to my email vishanth911@gmail.com
Thank you
Where does EC stands for in the hydroponics systems domain? Abbreviations can mean anything 
What physical quantity should be measured?
Sorry abt that.. EC stands for Electrical Conductivity
sort of ohm-meter ?
I dont know what an ohm meter is.. but i'm looking for a device which i can measure the mineral concentration in the hydroponic tank and get the reading to an Arduino board.
OK that is a clear goal:
Measuring the concentration of minerals is very difficult. There is probably no simple (e.g. linear) relation between the concentration of the minerals and the conductivity of the liquid. If there is only one mineral used you can make different concentrations, measure conductivity and create a lookup table. If you have two or more minerals it can be quite complicated. Conductivity will not discriminate between Na+ and K+ ions if they are both available.
To have a robust system you should have multiple sensors that are specific for some type of ion.
One thing I would at least consider is using a pH sensor as plants are sensitive for both too high and low pH.
NASA has a lot of knowledge, you can contact them at - http://natureandscienceagriculture.co.uk/Index/Pages/MAIN.html -
Thanks a lot.. But i am actually looking for an EC Meter(Electrical Conductivity) which i can connect to my Arduino board. Any idea where i can buy?
searching hydroponics in the upper right corner gave me this link - http://arduino.cc/forum/index.php/topic,81906.0.html -
There is an EC supplier mentioned - practicalmaker.com - This website is for sale! - practicalmaker Resources and Information. -
besides this link there were a dozen more related to hydroponics, have you read them?
Ya I have done a good research on it so far. Only prob i had was finding EC Meter. Thank a lot
Btw can this EC Shield be connected to Netduino as well?
Anyone who knows EC Meter for Neduino?
shields are often hardware compatible but you need to find the right drivers/libraries to get them working. Don't know the details of this shield as I cannot find its datasheet - I posted such a request on the site - no answer yet.
So no guarantees ..
Please let me know if u were able to find an EC Meter with any output which i can connect to the Arduino
Think you can make a basic (uncalibrated) electric conductivity meter quite easilily
GND -------C B------A----[ R1 ]----- +5V
A = analog in of Arduino.
B, C = connectors to hang into the water
R1 = potmeter - should be in the same order as resistance BC with a minimum of 1K
Water between B & C will have a certain conducticity or resistance. Together with R1 it forms a voltage divider.
If BC conducts well the analog port will read a LOW value and when BC has a HIGH resistance it will read a HIGH value.
try if this suites your need.
There a re several things here to consider, 1. Electrode materials must be made of the same materials and non reactive, Stainless steel is best as it 'generally' won't react with water or the chemicals used for fertilization. 2. The use of DC for sensing EC is not recommended as the conductive medium (solution or soil) WILL polarize or react to form a gas layer on the electrodes that will cause a small to medium drift in the EC measured. 3. EC is measured in Millisiemens, there is a wiki reference at Siemens (unit) - Wikipedia and 4. The 'common' home made electrodes are generally not so very usable if left in situ in the soil medium for those measurements I would recommend a Tensiometer or it's equivalent.
I designed EC meters in the late 90's to early 00's and we used a patented method for a portable EC meter that involved a frequency locked NE602, was stable after I finished. It had a datalogger and PH meter as options. The point I guess is, that what you want to do must be done in a clever manner as there are several 'Gotcha's' before you have designed a workable EC meter and that an accurate, repeatable and stable device is a non trivial task... Hope this helps and if you need more then message me.
I have done lots of tests connecting Arduino to a conductivity sensor and came up with this solution.
There are lots of things that can go wrong. For example
Electrode polarization. Designs where dc voltage is applied to the electrodes.
Length of the wire from sensor to Arduino.
Length of the sensor wire to the EC shield.
I designed my own sensor and transmitter and it works just fine. You can be 50ft away from the sensor and still register steady accurate conductivity values to Arduino Uno.
You may see it here
http://webpages.charter.net/tdsmeter/index.html
Well done, Very well done. The construction of an accurate EC meter is a most complex subject for the reasons I mentioned... Unfortunately expensive to buy "Off The Shelf" however your solution is repeat-able, calibrate able and... Do-able The hardest thing here is separating what you can understand from what you just don't know yet... Electronics is a Very Complex Subject and a Little Knowledge... can be Most Dangerous... Remember Mickey in the "Sorcerers Apprentice"... He knew how to start the Brooms... IMO
Doc
Here is a link for Arduino ec or conductivity sensors
http://webpages.charter.net/tdsmeter/products.html