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calculating conductivity of water by pi

Posted: Thu Apr 07, 2016 6:48 am
by anshuman95
hey guys
I have to make this college project in which, I was given to calculate tds and conductivity of water sample. and I have never worked on raspberry before but I have learned how to make a pi read analog values through mcp3008 but what I don't understand is how do I induct my conductivity electrode??

Re: calculating conductivity of water by pi

Posted: Thu Apr 07, 2016 3:01 pm
by experix
I guess you are asking how to connect the conductivity electrode to the ADC. Can you tell us about the electrode or post a link to its data sheet?

Re: calculating conductivity of water by pi

Posted: Thu Apr 07, 2016 4:01 pm
by brekee12
This is a bit more complicated than connecting the electrode to the ADC. Conductivity measurements based on AC voltage drop measurements. So what you need is an AC current generator and measure the voltage on the electrode or you need precise resistors and measure as a voltage divider. Both cases you need a rectifier between the electrode and the ADC. If it is possible use sinusoidal generator to avoid high freqvency components. The resistance you need to measure is between 10 Ohm and 1 MOhm which is not possible in one range, you need to handle range changes, too.

Re: calculating conductivity of water by pi

Posted: Fri Apr 08, 2016 9:22 pm
by liudr
Is your budget able to accommodate the correct AC measurement that brekee12 was describing:

http://www.atlas-scientific.com/product ... zo_ec.html

I saw small purple color fruit icons and teal infinity at the bottom of the page.