apogee SI-1H1 Infrared Radiometer Owner’s Manual

: June 3, 2024
: APOGEE

Table of Contents

SI-1H1 Infrared Radiometer
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SI-1H1 Infrared Radiometer

OWNER’S MANUAL
INFRARED RADIOMETER
Models SI-111, SI-121, SI-131, and SI-1H1
(including SS models)

TABLE OF CONTENTS

CERTIFICATE OF COMPLIANCE

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: SI-111, SI-121, SI-131, SI-1H1 Type: Infrared Radiometer

The object of the declaration described above is in conformity with the relevant Union harmonization legislation:

2014/30/EU 2011/65/EU

Electromagnetic Compatibility (EMC) Directive Restriction of Hazardous Substances (RoHS 2) Directive

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 cadmium, hexavalent chromium, lead, mercury, polybrominated biphenyls (PBB), polybrominated diphenyls (PBDE).

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, May 2016

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 SI series infrared radiometers consist of a thermopile detector, germanium filter, precision thermistor (for detector reference temperature measurement), and 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. SI-100 series 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 SI-100 Series SI-400 Series

Output Voltage SDI-12
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.

The four FOV options and associated model numbers are shown below:

SI-131

SI-121

SI-111

SI-1H1

SPECIFICATIONS

Approximate Sensitivity

SI-111
60 µV per C difference between target and detector temperature

SI-121
40 µV per C difference between target and detector
temperature

SI-131
20 µV per C difference between target and detector
temperature

SI-1H1
40 µV per C difference between target and detector
temperature

Output from Thermopile

Approximately -3.3 to 3.3 mV for a temperature
difference from -55 to 55 C

Approximately -2.2 to 2.2 mV for a temperature
difference from -55 to 55 C

Approximately -1.1 to 1.1 mV for a temperature
difference from -55 to 55 C

Approximately -2.2 to 2.2 mV for a temperature
difference from -55 to 55 C

Output from Thermistor
Input Voltage Requirement
Calibration Uncertainty (-20 to 65 C), when target and detector temperature are within 20 C

0.2 C

0 to 2500 mV (typical, depends on input voltage) 2500 mV excitation (typical, other voltages can be used)

0.2 C

0.3 C

0.2 C

Calibration Uncertainty (-40 to 80 C), when target and detector temperate are different by more than 20 C (see Calibration Traceability below)
Measurement Repeatability
Stability (Long-term Drift)

0.5 C

0.6 C

0.5 C

less than 0.05 C
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

Field of View
Spectral Range Operating Environment Dimensions Mass
Cable

22º half angle

18º half angle

14º half angle

32º horizontal half angle; 13º vertical
half angle

8 to 14 µm; atmospheric window (see Spectral Response below)

-55 to 80 C; 0 to 100 % relative humidity (non-condensing)

23 mm diameter; 60 mm length

190 g (with 5m of lead wire)
5 m of four conductor, shielded, twisted-pair wire; additional cable available in multiples of 5 m; santoprene rubber jacket (high water resistance, high UV stability, flexibility in cold conditions); pigtail lead wires

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

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
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-210 mounting bracket is recommended for mounting the sensor to a cross arm or pole. The AM-210 allows adjustment of the angle of the sensor with respect to the target and accommodates the radiation shield designed for all SI series 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.
A simple FOV calculator for determining target dimensions based on infrared radiometer model, mounting height, and mounting angle, is available on the Apogee website: http://www.apogeeinstruments.com/using-your-apogeeinstruments- infrared-radiometer/.

CABLE CONNECTORS

Apogee started offering in-line cable connectors on some bare-lead sensors in March 2018 to simplify the process of removing sensors from weather stations for calibration by not requiring the full cable to be uninstalled back to the data logger.

The ruggedized M8 connectors are rated IP67, made of corrosion-resistant marine-grade stainless-steel, and designed for extended use in harsh environmental conditions.
Instructions

Inline cable connectors are installed 30 cm from the head
(pyranometer pictured)

Pins and Wiring Colors: All Apogee connectors have six pins, but not all pins are used for every sensor. There may also be unused wire colors inside the cable. To simplify data logger connection, we remove the unused pigtail lead colors at the data logger end of the cable.

If you ever need a replacement cable, please contact us directly to ensure ordering the proper pigtail configuration.
Alignment: When reconnecting your sensor, arrows on the connector jacket and an aligning notch ensure proper orientation.

A reference notch inside the connector ensures proper alignment before tightening.

Disconnection for extended periods: When disconnecting the sensor for an extended period of time from a station, protect the remaining half of the connector still on the station from water and dirt with electrical tape or other method.

When sending sensors in for calibration, only send the short end of the cable and half the connector.

Tightening: Connectors are designed to be firmly finger-tightened only. There is an o-ring inside the connector that can be overly compressed if a wrench is used. Pay attention to thread alignment to avoid crossthreading. When fully tightened, 1-2 threads may still be visible.

Finger-tighten firmly

OPERATION AND MEASUREMENT
All SI-100 series radiometers output two signals: a voltage from the thermopile radiation detector (proportional to the radiation balance between target and detector) and a voltage from the thermistor (proportional to the magnitude of the excitation voltage and resistance of thermistor). The voltage output from the thermopile is an electrically-isolated bipolar (polarity is dependent on temperature difference between sensor and target) signal in the microvolt range and requires a high resolution differential measurement. The voltage output from the thermistor can be measured with a single-ended measurement. In order to maximize measurement resolution and signal-to-noise ratio, the input range of the measurement device should closely match the output range of the infrared radiometer. DO NOT connect the thermopile (white and black wires) to a power source. The detector is self-powered and applying voltage will damage it. Only the red wire should be connected to a power source.
VERY IMPORTANT: Apogee changed all wiring colors of our bare-lead sensors in March 2018 in conjunction
with the release of inline cable connectors on some sensors. To ensure proper connection to your data device, please note your serial number or if your sensor has a stainless-steel connector 30 cm from the sensor head then use the appropriate wiring configuration below.
Wiring for SI-100 Series with Serial Numbers range 0-7282
Red: High side of differential channel (positive thermopile lead) Black: Low side of differential channel (negative thermopile lead) Clear: Analog ground (thermopile ground) Green: Single-ended channel (positive thermistor lead) Blue: Analog ground (negative thermistor lead) White: Excitation channel (excitation for thermistor)
Wiring for SI-100 Series with Serial Numbers 7283 and above or has a cable connector
Red: Excitation channel (excitation for thermistor) Black: Low side of differential channel (negative thermopile lead) Clear: Shield/Ground Green: Single-ended channel (positive thermistor lead) Blue: Analog ground (negative thermistor lead) White: High side of differential channel (positive thermopile lead)

Sensor Calibration Apogee SI series infrared radiometers are calibrated in a temperature controlled chamber that houses a custombuilt 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 (12 C), above (18 C), and equal to the detector temperature. The range of detector temperatures is -15 C to 45 C (set points at 10 C increments). Data are collected at each detector temperature set point, after detectors and target reach constant temperatures. All Apogee analog infrared radiometer models (SI-100 series) have sensor-specific calibration coefficients determined during the custom calibration process. Unique coefficients for each sensor are provided on a coefficient certificate (example shown below).
Calibration overview data are listed in box in upper left-hand corner, sensor specific calibration coefficients are listed in box in upper right-hand corner, temperature errors are shown in graph, and calibration date is listed below descriptions of calibration procedure and traceability.

RT

24900

VE X VO U T

1

(1)

TK

A

1 Bln( RT ) C(ln( RT ))3

TC TK 273.15 .

(3)

TT 4 TD 4 m SD b

m C2 TD 2 C1 TD C0 b C2 TD 2 C1 TD C0