Actually, the problem is whether sensing air humidity is the same as sensing the proportion of the water in sand.
If I penetrate a probe with a capacitive humidity sensor on the tip in sand , would I have measured humidity of sand?
Or what I am trying to do is measure volumetric water content of sand?
Any comment?
I guess not.
There is such a thing as water absorption
of aggregates. In this case the aggregates
is sand. Ask any civil engineer he/she may be
able to explain better.
I would use a simple resistance meter, the probes just pushed into the agrigate. The type I am thinking of the ones Builder use to access the dampness of walls.
Very simple to design and calibrate You can make all your experiments of range using a multimeter and then build a simple meter using your resultes.
Barrybear
I notice that people who need to lay underground pipe usually meausure the resistance of soil as a metric for determining how susceptible to corosion the soil is.
The more water contents, the more it is susceptible to corosion.