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Does your soil have no salts or minerals like Styrofoam beads?.
Yes absorption/reflection. For light there is an example ir light sensors with emitter and receiver ir led's.
Paralell pcb plates act as small antena cylindrical pattern. It starts detecting hand reflection at 15cm. Maybe a 15cm antenna range..
Most linear to measure and transparent to minerals is 380-485MHz range
I agree that the quoted diagram emphasizes the importance of a complex impedance measurement. But the real part of ε is not the "lossy part", it's the imaginary part of permittivity that represent the losses https://en.wikipedia.org/wiki/Permittivity#Complex_permittivityTrue, but what the authors in the paper are reporting is the real part of the dielectric constant (lossy part) and happily ignoring the imaginary part of the dielectric constant.
Hi, for new design I recommend this setup.
View attachment 129297
This will adjust better range because AD8307 is logarithmic. So find better range for probe on wet and probe dry. Adjust R until get most difference between wet to dry probe voltage output.
If you do not want 100MHz or 80MHz you can use any oscillator. I tested at 100khz with 2cm range. But not transparent to minerals.Good results only for tap water no nutrients added. 400ppm
Regards,
Vitor
One oscillator at 80MHz connected to one wire probe and other pcb wire connected to a detector?
Or is it using RC constant time and two pcb wires acts as capacitor, but injecting 80Mhz in circuit?
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