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.
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).
SENSOR MODELS Model Output SI-100 Series Voltage SI-400 Series 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.
SPECIFICATIONS SI-111 SI-121 SI-131 SI-1H1 Approximate Sensitivity 60 µV per C difference between target and detector temperature 40 µV per C difference between target and detector temperature 20 µV per C difference between target and detector temperature 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.
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).
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.
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.
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).
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.
V R T 24900 EX 1 VOUT TK (1) 1 A B ln( R T ) C(ln( R T ))3 TC TK 273.15 .
TT TD m S D b 4 4 m C2 TD C1 TD C0 2 b C2 TD C1 TD C0 2 TT TD m S D b 4 1 4 273.
TSensor TT arget 1 TBackground 4 4 TSensor 1 TBackground 4 TT arg et 4 4 4
MAINTENANCE AND RECALIBRATION 1. 2. 3. 4.
TROUBLESHOOTING AND CUSTOMER SUPPORT
