Salt Water Sensor

[swuest]

I'm looking for probes that react and sense salt water. Something like what the McMurdo EPIRB has. I can't seem to find anything like that. I would appreciate any help you have to offer. Thank you!

 

[(*steve*)]

A metallic sodium probe will detect water and react.

However, I guess that's not the reaction you want.

If it's salt water then any two metal probes will allow you to measure conductance. Dissimilar metals will cause a small voltage to be generated.

My favourite technique is to drive one probe with a square wave (via a 10nf capacitor) and to detect it at the other probe. There's some nifty CMOS circuits to do this. It has the advantage of removing any DC component which would lead to the premature corrosion of one or other of the probes.

 

[Wabajig]

If you want something more automated, I would look up a comparator circuit. You'll have to do the research on part and voltage supply you have on hand. So, on one input is your voltage divider with you probe acting as one resistor to ground, and the other input could be tied to the center lead of a 10K pot. The output goes high when the + input goes above the - input. The output could be tied to a buzzer or LED depending on voltage. Like I said you'll need to do a little research.