Been doing some experimenting with some new equipment as I get ready to try some new crops....
Capacitive moisture sensor
Buried in some soaked and drained coco coir.
You would think that it would have an extremely high moisture content - but coir has an amazing air holding capacity... The moisture content is just over 30%.
ETA: Whoops!!!! I made a major math error in the coding of my controller which is providing those readouts.... Turns out that the humidity was more like 33% and the moisture was more like 82% - which is still good air holding capacity considering that it was completely saturated.