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Revision as of 02:21, 4 May 2011 by (talk | contribs) (How an optode works)
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Introduction to dissolved oxygen

Why is oxygen important? For us humans, if we have oxygen, we survive...yay! If not, we don' So, superficially, this may not seem like a very important parameter to know - you either have oxygen, or you don't. However, for many microorganisms, there are a lot of shades of gray.

For a bacteria or a yeast, different amounts of oxygen produce different results. For instance, starving a yeast cell of oxygen produces ethanol as a metabolite product instead of carbon dioxide. Starving a lake of oxygen not only prevents fishies from living in it, but also promotes the formation of large algae surfaces. Cool, right?

The biggest problem with measuring dissolved oxygen currently is the cost of the equipment available to do it. Typically, dissolved oxygen probes run well into the $400+ range, thus placing them well out of the realm of hobbyists. The cost is not wholly unwarranted - dissolved oxygen meters used a platinum catalyzed reaction with very specific membranes to measure oxygen response. By cutting out the platinum catalyst and the specialized membrane, the cost of a DO meter could drop considerably...enter the optode!

Building a dissolved oxygen probe

How an optode works

In order to reduce cost, we'll be building a dissolved oxygen optode instead of the more common dissolved oxygen electrode.

In an electrode, a small change in a voltage or current is used to detect a change in oxygen concentration. In an optode, a small change in reflected light intensity is used to detect changes in oxygen concentration:

What you need

How to build it

Things to keep in mind

Interfacing and measuring

Calibrating a home-built optode

Making it cooler

Geeking out