SI-111
Precision Infrared Radiometer
Th e SI-111* is a precision, infrared radiometer that
makes continuous measurements in fi eld conditions.
Infrared temperature sensors provide a non-contact
means of measuring the surface temperature of an ob-
ject or surface by sensing the infrared radiation given
off by the subject. Th is unique sensor is manufactured
by Apogee Instruments Inc. (Logan, UT).
Typical applications include:
Road surface temperature•
Plant canopy temperature for irrigation scheduling •
and crop water stress
Soil, snow, and water surface temperatures•
The SI-111 is comprised of a thermopile, which
measures surface temperature, and a thermistor,
which measures sensor body temperature. The
two temperature probes are housed in a rugged
aluminum body that contains a germanium window.
When compared with the silicon window of its
predecessor, the germanium window facilitates
correction of target emissivity, reduces the effect
of atmospheric humidity, and allows the sensor to
be used at greater distances from the target.
Both the thermopile and the thermistor output a
millivolt signal. Our dataloggers measure the milli-
volt signals and apply the Stefan-Boltzman equation,
which corrects for the eff ect of sensor body tempera-
ture on the target temperature. Use of the Stefan-
Boltzman equation allows the SI-111 to achieve an
absolute accuracy of ±0.2°C from -10° to 65°C.
Mounting
The SI-111 is often mounted to a CM202, CM204,
or CM206 crossarm, a tripod or tower mast, or a
user-supplied pole via a CM220 Right Angle Mount
or CM230 Adjustable Inclination Mount. Th e SI-111
should be mounted perpendicular to the target
surface. Therefore, the CM230 mount is recom-
mended when the target surface is on an incline.
Th e SI-111 may also be mounted directly to a user-
supplied camera tripod.
The SI-111 is mounted to a CM204 crossarm
via the CM230; the CM230 allows the sensor
to be pointed at the surface of interest.
The SI-111 is mounted to a CM204 crossarm
via the CM220 Right Angle Mount.
*Prior to November 2008, the SI-111 was named the IRR-P.
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Ordering Information
Model Description
SI-111 Precision Infrared Radiometer with 15-ft cable
SI-111-PW Precision Infrared Radiometer with 15-ft
cable and connector for attaching sensor to
a prewired enclosure.
Mounting Hardware
CM220 Right Angle Mount
CM230 Adjustable Angle Mounting Kit that allows
the SI-111 to be pointed at the surface of
interest
CM202 Two-foot crossarm that attaches the CM220
or CM230 to a tripod or tower
CM204 Four-foot crossarm that attaches the CM220
or CM230 to a tripod or tower
CM206 Six-foot crossarm that attaches the CM220 or
CM230 to a tripod or tower
CM210 Bracket
Aluminum Pipe
The CM202 (shown), CM204, and CM206 crossarms consist
of a 1” IPS anodized aluminum pipe and a CM210 bracket
that attaches to the tripod or tower.
Specifi cations
Datalogger Channels:
one diff erential (thermopile) and one single-ended
(thermistor); please note that our CR200-series
dataloggers are not compatible.
Input Power:
2.5 V excitation for thermistor
Absolute Accuracy:
±0.2°C @ -10° to +65°C; ±0.5°C @ -40° to +70°C
Uniformity:
±0.1°C @ -10° to +65°C; ±0.3°C @ -40° to +70°C
Repeatability:
±0.05°C @ -10° to +65°C; ±0.1°C @ -40° to +70°C
Response Time:
<1 s to changes in target temperature
Target Temperature Output Signal:
60 μV per °C diff erence from sensor body
Body Temperature Output Signal:
0 to 2500 mV
Optics:
Germanium lens
Wavelength Range:
8 to 14 μm (corresponds to atmospheric window)
Field of View (FOV):
22° half angle. Th e FOV is reported as the half-angle
of the apex of the cone formed by the target (cone
base) and the detector (cone apex). Th e target is a
circle from which 98% of the radiation viewed by the
detector is being emitted.
Operating Range: -55° to +80°C; 0 to 100% RH
Cable Description:
15’ (4.5 m) twisted, shielded 4-conductor wire
with Santoprene casing, ending in pigtails.
Dimensions:
0.9” (2.3 cm) diameter, 2.4” (6 cm) length
Weight:
6.7 oz. (190 g)
SI-111Half Angle
Target Distance
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Copyright © 2006, 2009
Campbell Scientifi c, Inc.
Printed April 2009