Water Sensors

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bman87
 
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Joined: Mon Mar 26, 2012 11:28 am

Water Sensors

Post by bman87 »

Does anyone know where I can find a sensor for testing water? Specifically I am looking to test pH levels.

I am starting a project to automate an indoor hydroponics system

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easternstargeek
 
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Joined: Mon Dec 13, 2010 1:39 pm

Re: Water Sensors

Post by easternstargeek »

Hi!

Measuring pH is done all the time, using a special probe containing a calibrated reference solution and some magic electrodes.

I suggest you start by reading up on pH measurement techniques. The best place to read about measuring ANYTHING is Omega Instruments:

http://www.omega.com

Specifically this tutorial on pH measurement probe basics:
http://www.omega.com/toc_asp/BANNED.h ... basics_REF

Before you get too far, please be aware that pH instrumentation (that is any good) is pretty expensive, no matter where you get it. You can be in for well over $US100.00 by the time you get a probe and preamplifier/indicator.

A raw probe acts like an ultra high-impedance voltage source in the millivolt range, and can't really drive any kind of indicator (even a DMM) directly without being loaded-down and introducing substantial measurement errors. You will need a front-end pre-amp that can work with a signal source of well over 100 gigohms. At that level of performance, everything becomes a problem- wire, insulation, connectors, circuit board dielectric and layout etc. Fortunately, pre-amplified probe heads are available that contain an impedance converter- you will still get millivolt signals, but at a nice, low buffered impedance that can easily drive more conventional instrument front-ends.

Depending what you want to do with the signal (Arduino Analog in, maybe?) you'll have to boost it some more, but a simple DIY op-amp circuit will work just fine.

Read up, first, and if you have anymore questions, post them here.
Good luck!

thefatmoop
 
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Joined: Tue Aug 19, 2008 4:36 pm

Re: Water Sensors

Post by thefatmoop »

http://www.sparkfun.com/products/10972

includes example code for arduino too. If this is for you just be warned that they are EXTREMELY fragile. not only that, but the probing end can't dry out if I remember correctly.

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