Campbell Scientific Sentek EnviroSCAN EasyAG SDI-12 Manual v 3.4 - Manual (Page 29)

EnviroSMART & EasyAG SDI-12 Probe Manual
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Figure 10: Measurements using imperial units
What part of the soil profile do multiple sensors on the probe
measure?
Probes in almost all cases have more than one sensor to monitor the depth of irrigation and the depth
of the root zone. The first sensor is located at a soil depth of 10cm (if the datum plate of the top cap
sits on ground level) measuring effectively the soil profile slice of 5-15cm depth. The next sensor is
located at 20 cm measuring effectively 15 –25cm soil depths. With further sensors at 10cm intervals on
the probe rod, the measurement depth would be respectively (25-35cm, 35-45cm and so on).
If you raise the datum plate of the top-cap 5cm above the ground surface, placing the center of the first
sensor effectively at 5cm soil depth, the sphere of influence of the sensor will measure a soil slice from
0-10cm. For the other sensors at 10cm depth intervals on the probe rod, the measurement depth would
be respectively (20-30cm, 30-40cm and so on).
Figure 11: Measurements of multiple sensors on the probe