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Covert Soil Profile Sensor (CSPS)
 The Idaho National Engineering and Environmental Laboratory (INEEL)
has developed a covert soil profile sensor (CSPS) system for use with
landfill caps. This system utilizes an inductive antenna to not only
communicate with the interrogating system but to provide power for it,
thus eliminating the need for batteries in the buried sensor. The
sensors supported at the present time are moisture, pressure and
temperature. Other types of sensors can be employed, depending upon
power requirements and interface needs.
The process of extracting data from this system involves the
deployment of a large, 5 ft. diameter, inductive loop. This loop is laid
on the ground near or over the buried sensor. The loop is energized at a
specific frequency and transmits energy to the inductive coil inside the
buried sensor. The buried sensor contains an inductive coil, a diode and
a capacitor that rectifies and stores the energy from the inductive
coil. This is the same technique used in electric toothbrushes except
that here a capacitor replaces the battery. After the sensor capacitor
is charged, the sensor automatically makes a measurement. The inductive
loop then sends a command to the sensor to transmit its data. The data
is transmitted via an FM serial data stream. The loop must remain in
place for the entire transmission. After successful interrogation, the
loop must be moved to the next buried sensor.
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