Soil moisture

[Bern1937]

I want to measure the amount or level of moisture in dirt. This will be a long term system, so don't want to use the normal conductivity system because of plating or build-up on the electrodes. Thinking about using the capacity measuring type of sensors/monitors. In reading many articles there are numerous methods and frequencies suggested. My question: Anybody have knowledge and experience on doing this, and what are some ideas, suggestions, and/or best way to think about? What worked for you, and any thoughts?

Also thinking about using conductivity, and by using a pulse with very low duty cycle would minimize the plating action. But wouldn't I still have some corrosion build up just due to the probes sitting in moist dirt?

Thanks

 

[Bluejets]

With the capacitive measure, the probes are electrically insulated from the surroundings so no risk of any corrosion there.
Unless of course your insulation breaks down over time.
Most of the capacitive probe modules will require the use of an Arduino microcontroller.

The alternative is the standard probe system using a pulses signal which is a kind of AC which they claim doesn't have probe errosion problem.
Circuit below is actually a water level sensor but should work for moisture also.

 

[Bern1937]

Thanks, Bluejets. With the probes like you mentioned, there still would be corrosion after sitting there for months on end, I think. With the caps connected to the probes, that way, at least problems from DC current causing plating, would be stopped. I'm thinking I could build my own probes, and stay analog all the way. I would like the info. to read out on a meter and also trip a relay. That part is simple. I am just scratching my head on the sensor/probe part.

 

[Bluejets]

With the probes like you mentioned, there still would be corrosion after sitting there for months on end, I think.

Not if stainless steel, and as already explained, there is no DC on the probes in the circuit provided.

As far as capacitive modules, you could go for these from say Ebay for example but you still need to add Arduino control, write the program and physically enclose the controls away from external moisture etc.
Analog reading would need to be averaged as they tend to drift around a lot.
No requirement to build your own sensor as everything is in the module.
Some say adding some epoxy along the sides of the board is advised.

Tutorial here............. https://create.arduino.cc/projecthu...r-with-soil-capacitive-sensor-tutorial-78f80c