Campbell Scientific Sentek EnviroSCAN EasyAG SDI-12 Manual v 3.4 - Manual (Page 28)

EnviroSMART & EasyAG SDI-12 Probe Manual
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Appendix A – Soil Moisture Management
What soil volume does the SDI-12 probe interface measure at a
single sensor?
At a single depth level, a sensor on the probe records volumetric water content from a soil volume
outside the access tube, which has a sphere of influence of:
⇒ 10cm vertical height
⇒ 5-10cm radial distance from the outer wall of the access tube
What are the water units?
If a calibrated sensor reads one(1) millimetre, there is one(1) millimetre of volumetric water content in a
soil volume 10cm deep.
Q. What does 1mm volumetric water content / 10cm soil depth mean?
A. You require one(1) litre of water to cover one(1) square meter (m²) to a soil depth of one(1)
millimetre.
Figure 9: Measurements using metric units