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# Inexpensive conductivity probe Step 1 - Sensor Probe design (revised)

by roberts_ecofarm | 31 Oct 16:55

Here are some sketches for a couple of probes I'm going to test. I'm planning on housing the probe in a three inch PVC elbow because that will be easy to attach to the domestic plumbing between the well and any water treatment. The same probe housing should be usable in springs and streams to monitor surface water.

Feedback or ideas around probe geometry is appreciated.

(Revised... I left out the Temperature sensor on the original drawings)

So, on paper these designs look like they will work. Next step will be to build one and see what happens when design meets the real world. Hoping for a build that is not to complicated and easily replicated.

Any thoughts before I head to the hardware store?

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So, after reviewing my drawings I discovered I'd made a huge mistake on the cell constant (K) in the two post probe design. The cell I designed would have a K value of 100 not 1. So I'm redesigning using electrical spade connectors. The equation for calculating K is K= L/A where L is the distance between the posts and A is the area of the post in cm. A spade connector will give me an area of A=0.51sq.cm. so if I put the posts 1/2 cm apart L will be .5 cm. That gives me a K of .98 which is right where it needs to be.

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