24
Electronics in the TDR 150 generate and sense the return
of a high energy signal that travels down and back,
through the soil, along the waveguide composed of the
two replaceable, stainless steel rods. The sampling volume
is an elliptical cylinder that extends approximately 3 cm
out from the rods. The high frequency signal information
is then converted to volumetric water content. High
amounts of clay or high electrical conductivity
(EC>2 mS/cm) will attenuate the high
-
frequency signal
and affect the reading displayed by the meter. Very high
organic matter content will similarly affect the VWC read-
ing.
GPS Status
*
For best results, wait until the GPS has located as many
satellites as possible. When GPS is enabled and the loca-
tion is fixed, the icon will change from white, to gray, to
black. A black icon indicates the meter has detected 10 or
more satellites. If differential correction is available, the
GPS icon will include a crosshairs icon as well.
GPS coverage will be best when you have a clear view of
the sky. The GPS receiver is in the front of the meter (near
the USB port). When taking readings, the receiver should
be pointed away from any structures or other obstacles
such as trees.
*
GPS only available with upgraded units (p. 15).
