Why is the output of the ECHO probe similar when it is buried in saturated soil and submerged in water?
The ECHO probe’s optimal range is from oven dry to saturated water content. Above saturation, the change in probe output with increasing water content is near 0. The ECHO probe uses an electro-magnetic (EM) field to sense the dielectric of the surrounding medium. As water content increases, the width of that EM field diminishes somewhat. As it approaches 100% VWC (water with no soil), the EM field diminishes to a fraction of its original size, and primarily senses the probe surface itself.
