Apogee SIL-411 User manual

APOGEE INSTRUMENTS, INC. | 721 WEST 1800 NORTH, LOGAN, UTAH 84321, USA
TEL: (435) 792-4700 | FAX: (435) 787-8268 | WEB: APOGEEINSTRUMENTS.COM
Copyright © 2020 Apogee Instruments, Inc.
OWNER’S MANUAL
COMMERCIAL INFRARED
RADIOMETER
Models SIL-411
Rev: 28-Oct-2020

TABLE OF CONTENTS
Owner’s Manual ............................................................................................................................................................................... 1
Declaration of Conformity ....................................................................................................................................................... 3
Introduction ............................................................................................................................................................................. 4
Sensor Models ......................................................................................................................................................................... 5
Specifications ........................................................................................................................................................................... 6
Deployment and Installation.................................................................................................................................................... 7
Operation and Measurement .................................................................................................................................................. 9
Maintenance and Recalibration............................................................................................................................................. 17
Troubleshooting and Customer Support................................................................................................................................ 18
Return and Warranty Policy................................................................................................................................................... 19

DECLARATION OF CONFORMITY
EU Declaration of Conformity
This declaration of conformity is issued under the sole responsibility of the manufacturer:
Apogee Instruments, Inc.
721 W 1800 N
Logan, Utah 84321
USA
for the following product(s):
Models: SIL-411
Type: Infrared Radiometer
The object of the declaration described above is in conformity with the relevant Union harmonization legislation:
2014/30/EU Electromagnetic Compatibility (EMC) Directive
2011/65/EU Restriction of Hazardous Substances (RoHS 2) Directive
2015/863/EU Amending Annex II to Directive 2011/65/EU (RoHS 3)
Standards referenced during compliance assessment:
EN 61326-1:2013 Electrical equipment for measurement, control and laboratory use –EMC requirements
EN 50581:2012 Technical documentation for the assessment of electrical and electronic products with respect to
the restriction of hazardous substances
Please be advised that based on the information available to us from our raw material suppliers, the products
manufactured by us do not contain, as intentional additives, any of the restricted materials including lead (see
note below), mercury, cadmium, hexavalent chromium, polybrominated biphenyls (PBB), polybrominated
diphenyls (PBDE), bis(2-ethylhexyl) phthalate (DEHP), butyl benzyl phthalate (BBP), dibutyl phthalate (DBP), and
diisobutyl phthalate (DIBP). However, please note that articles containing greater than 0.1% lead concentration are
RoHS 3 compliant using exemption 6c.
Further note that Apogee Instruments does not specifically run any analysis on our raw materials or end products
for the presence of these substances, but rely on the information provided to us by our material suppliers.
Signed for and on behalf of:
Apogee Instruments, October 2020
Bruce Bugbee
President
Apogee Instruments, Inc.

INTRODUCTION
All objects with a temperature above absolute zero emit electromagnetic radiation. The wavelengths and intensity
of radiation emitted are related to the temperature of the object. Terrestrial surfaces (e.g., soil, plant canopies,
water, snow) emit radiation in the mid infrared portion of the electromagnetic spectrum (approximately 4-50 µm).
Infrared radiometers are sensors that measure infrared radiation, which is used to determine surface temperature
without touching the surface (when using sensors that must be in contact with the surface, it can be difficult to
maintain thermal equilibrium without altering surface temperature). Infrared radiometers are often called infrared
thermometers because temperature is the desired quantity, even though the sensors detect radiation.
Typical applications of infrared radiometers include plant canopy temperature measurement for use in plant water
status estimation, road surface temperature measurement for determination of icing conditions, and terrestrial
surface (soil, vegetation, water, snow) temperature measurement in energy balance studies.
Apogee Instruments SIL-111 infrared radiometers consist of a thermopile detector, germanium filter, precision
thermistor (for detector reference temperature measurement), signal processing circuitry mounted in an anodized
aluminum housing, and a cable to connect the sensor to a measurement device. All radiometers also come with a
radiation shield designed to minimize absorbed solar radiation, but still allowing natural ventilation. The radiation
shield insulates the radiometer from rapid temperature changes and keeps the temperature of the radiometer
closer to the target temperature. Sensors are potted solid with no internal air space and are designed for
continuous temperature measurement of terrestrial surfaces in indoor and outdoor environments. The SIL-111
sensors output an analog voltage that is directly proportional to the infrared radiation balance of the target
(surface or object the sensor is pointed at) and detector, where the radiation balance between target and detector
is related to the temperature difference between the two.

SENSOR MODELS
Model
Output
SIL-411
SDI-12
SIL-111
Voltage
Sensor model number and serial number are
located on a label near the pigtail leads on the
sensor cable. If you need the manufacturing date
of your sensor, please contact Apogee Instruments
with the serial number of your sensor.

SPECIFICATIONS
Calibration Traceability
Apogee SI series infrared radiometers are calibrated to the temperature of a custom blackbody cone held at
multiple fixed temperatures over a range of radiometer (detector/sensor body) temperatures. The temperature of
the blackbody cone is measured with replicate precision thermistors thermally bonded to the cone surface. The
precision thermistors are calibrated for absolute temperature measurement against a platinum resistance
thermometer (PRT) in a constant temperature bath. The PRT calibration is directly traceable to the NIST.
Spectral Response
SIL-411
Input Voltage Requirement
5.5 to 24 V DC
Current Drain
1.5 mA (quiescent), 2.0 mA (active)
Calibration Uncertainty (0 to 50 C),
when target and detector
temperature are within 20 C
0.5 C
Measurement Repeatability
Less than 0.05 C
Stability (Long-term Drift)
Less than 2 % change in slope per year when germanium filter is maintained in a
clean condition (see Maintenance and Recalibration section below)
Response Time
0.6 s, time for detector signal to reach 95 % following a step change; fastest data
transmission rate for SDI-12 circuitry is 1 s
Field of View
22° half angle
Spectral Range
8 to 14 µm; atmospheric window (see Spectral Response below)
Operating Environment
-55 to 80 C; 0 to 100 % relative humidity (non-condensing)
Dimensions
23 mm diameter, 60 mm length
Mass
190 g (with 5m of lead wire)
Cable
5 m of six conductor, shielded, twisted-pair wire; TPR jacket (high water resistance,
high UV stability, flexibility in cold conditions); pigtail lead wires
Spectral response of SI series infrared
radiometers. Spectral response (green line) is
determined by the germanium filter and
corresponds closely to the atmospheric window
of 8-14 µm, minimizing interference from
atmospheric absorption/emission bands (blue
line) below 8 µm and above 14 µm. Typical
terrestrial surfaces have temperatures that yield
maximum radiation emission within the
atmospheric window, as shown by the blackbody
curve for a radiator at 28 C (red line).

DEPLOYMENT AND INSTALLATION
The mounting geometry (distance from target surface, angle of orientation relative to target surface) is
determined by the desired area of surface to be measured. The field of view extends unbroken from the sensor to
the target surface. Sensors must be carefully mounted in order to view the desired target and avoid including
unwanted surfaces/objects in the field of view, thereby averaging unwanted temperatures with the target
temperature (see Field of View below). Once mounted, the green cap must be removed. The green cap can be
used as a protective covering for the sensor, when it is not in use.
An Apogee Instruments model AM-250 mounting bracket is recommended for mounting the sensor to a cross arm
or pole. The AM-250 allows adjustment of the angle of the sensor with respect to the target and accommodates
the radiation shield designed for SIL-111 infrared radiometers.

Field of View
The field of view (FOV) is reported as the half-angle of the apex of the cone formed by the target surface (cone
base) and the detector (cone apex), as shown below, where the target is defined as a circle from which 98 % of the
radiation detected by the radiometer is emitted.
Sensor FOV, distance to target, and sensor mounting angle in relation to the target will determine target area.
Different mounting geometries (distance and angle combinations) produce different target shapes and areas, as
shown below.
Model
Half Angle
Mounting Height (m)
FOV Area (m²)
0°
45°
60°
SIL-111
22°
1.0
0.51
1.90
11.26
SIL-111
22°
2.0
2.05
7.58
45.0
SIL-111
22°
3.0
4.62
17.1
101.3
A simple FOV calculator for determining target dimensions based on infrared radiometer model, mounting height,
and mounting angle, is available on the Apogee website: https://www.apogeeinstruments.com/irr-calculators.

OPERATION AND MEASUREMENT
All SIL-411 radiometers have an SDI-12 output, where target and detector temperatures are returned in digital
format. Measurement of SIL-411 series radiometers requires a measurement device with SDI-12 functionality that
includes the M or C command.
Wiring for SIL-411
White: SDI-12 Data Line
Red: Power In (4.5-24 V DC)
Black: Ground (for sensor signal and input power)
Clear: Shield/Ground

Sensor Calibration
Apogee SIL-111 infrared radiometers are calibrated in a temperature-controlled chamber that houses a custom-
built blackbody cone (target) for the radiation source. During calibration, infrared radiometers (detectors) are held
in a fixture at the opening of the blackbody cone, but are thermally insulated from the cone. Detector and target
temperature are controlled independently. At each calibration set point, detectors are held at a constant
temperature while the blackbody cone is controlled at temperatures below (10 C), above (10 C), and equal to the
detector temperature. The detector temperatures are 10, 25, and 40. Data are collected at each detector
temperature set point, after detectors and target reach constant temperatures.
All Apogee SIL-411 SDI-12 infrared radiometers have sensor-specific calibration coefficients determined during the
custom calibration process. Coefficients are programmed into the microcontroller at the factory. Calibration data
for each sensor are provided on a calibration certificate (example shown on following page).
Calibration overview data are listed in box in upper left-hand corner, temperature errors are shown in graph, and
calibration date is listed below descriptions of calibration procedure and traceability.
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