Although there are ways to get around this, a 2022 paper by Maja Škiljo and colleagues in Sensors covers an interesting way to make use of this signal attenuation property of changing moisture ...
With NIR moisture sensors, operators will be able to instantly and continuously measure ash moisture and control these problems. Preventing airborne dust and controlling the weight of the ash ...
However, by measuring the length of time taken for the microwaves to return to the sensor, the distance to each material in the wall can be calculated ... and then compared the results to measurements ...