Electronic – function to model the resistance between 2 metal probes


I'm trying to design something that will measure the amount of rainfall in a small container. And I was wondering if there was a function I could use to calculate the resistance of the metal probes when say we've had 5ml of rain and then 25ml of rain.

With the output of these probes I can put these in a potiential divider and then a have a voltage output proportional to the amount of rainfall.

Is this a sensible approach to measure the amount of rainfall electronically?

Best Answer

I'm not sure that will work well; you probably won't see a factor 5 difference between 5 ml and 25 ml.

I would suggest something capacitive. The relative permittivity of water is about 80 times that of air, so you should be able measure a difference in capacitance between two plates with water between them compared to air. So the capacitance will be a linear function of immersion level. The advantage of the (insulated) plates is that you won't get electrolytic effects.