Sentek RT6, Руководство по оборудованию

Страница: 25 / 90

CHAPTER 3: TECHNICAL DESCRIPTION
Page 21
A computer is connected to the logging facility to
configure the system and set the time/date clock. The
configuration is stored in the removable loggers non-
volatile memory which includes:

Number of sensors on Run A

Number of sensor on Run B

Sampling interval

Logger ID
Probe
Each EnviroSCAN/EasyAG probe comprises one or
more soil moisture sensors placed along a support
rod. The probe, usually with an array of multiple
sensors, is installed into a vertical PVC access tube at
representative locations.
During sampling the logger applies power to the
probes and a signal to power up (address) a particular
sensor. The address signal is processed by the
interface (5-wire board) which applies power down
one of the wires of the ribbon cable. The sensor that
has been addressed (via PCB link) picks up the power
from the ribbon cable and begins to oscillate
depending on moisture content of the soil. The signal
from the sensor (open collector 40 to 80 kHz) is
applied to a common wire on the ribbon cable back to
the interface board.
The 5-wire interface board converts the signal from
open collector to differential drivers (RS485 type) for
transmission back to the logger via probe cabling.
Sensor
The principle of operation of the
EnviroSCAN/EasyAG soil moisture sensor is based
on capacitance.
A capacitor consists of two conductive plates
separated by an insulating material (dielectric). The
value of capacitance (C) is determined by the area of
the plates, distance between the plates and the