SI-111 and SI-111SS Precision Infrared Radiometers
4
7.
Select the measurement and its associated output options.
8.
Click
Finish
and save the program. Send the program to the datalogger if
the datalogger is connected to the computer.
9.
If the sensor is connected to the datalogger, check the output of the sensor
in the data display in
LoggerNet
,
PC400,
RTDAQ
, or
PC200W
to make
sure it is making reasonable measurements.
5. Overview
The SI-111 and SI-111SS sense the infrared radiation emitted by the target and
determines surface temperature of the target without physical contact. With
contact sensors, it is difficult to avoid influencing the temperature, maintain
thermal contact, and provide a spatial average. By mounting infrared sensors at
an appropriate distance from the target, they can measure an individual leaf, a
canopy, or any surface of interest.
The SI-111 and SI-111SS consist of a thermopile, which measures surface
temperature, and a thermistor, which measures sensor-body temperature. The
two temperature sensors are housed in a rugged aluminum body that contains a
germanium window.
Both the thermopile and the thermistor output a millivolt signal that most of
our dataloggers can measure. The datalogger uses the Stefan-Boltzman
equation to correct for the effect of sensor body temperature on the target
temperature. The corrected readings yield an absolute accuracy of ±0.2 °C
from –10 to 65 °C.
The field-of-view for infrared sensors is calculated based on the geometry of
the sensor and lens. The SI-111 and SI-111SS have a 22-degree half angle field
of view (FOV). The FOV is reported as the half-angle of the apex of the cone
formed by the target (cone base) and the detector (cone apex). The target is a
circle from which 98% of the radiation viewed by the detector is being emitted.