Description

One of the most important steps in using an infrared radiometerfrom Apogee instruments is determining the exact field of view ofthe sensor during installation. The mounting geometry (distancefrom target surface, angle of orientation relative to targetsurface) is determined by the desired area of surface to bemeasured. The field of view extends unbroken from the sensor to thetarget surface. Sensors must be carefully mounted in order to viewthe desired target and avoid including unwanted surfaces/objects inthe field of view, thereby averaging unwanted temperatures with thetarget temperature. The FOV Calculator makes this process simple.To use the calculator, simply enter your IRR viewing height (H),viewing angle (θ, relative to nadir view = 0°), chose your sensormodel, then click calculate. General Information: All objects witha temperature above absolute zero emit electromagnetic radiation.The wavelengths and intensity of radiation emitted are related tothe temperature of the object. Terrestrial surfaces (e.g., soil,plant canopies, water, snow) emit radiation in the mid infraredportion 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 thesurface (when using sensors that must be in contact with thesurface, it can be difficult to maintain thermal equilibriumwithout altering surface temperature). Infrared radiometers areoften called infrared thermometers because temperature is thedesired quantity, even though the sensors detect radiation. Typicalapplications of infrared radiometers include plant canopytemperature measurement for use in plant water status estimation,road surface temperature measurement for determination of icingconditions, and terrestrial surface (soil, vegetation, water, snow)temperature measurement in energy balance studies. ApogeeInstruments SI series infrared radiometers consist of a thermopiledetector, germanium filter, precision thermistor (for detectorreference temperature measurement), and signal processing circuitrymounted in an anodized aluminum housing, and a cable to connect thesensor to a measurement device. All radiometers also come with aradiation shield designed to minimize absorbed solar radiation, butstill allowing natural ventilation. The radiation shield insulatesthe radiometer from rapid temperature changes and keeps thetemperature of the radiometer closer to the target temperature.Sensors are potted solid with no internal air space and aredesigned for continuous temperature measurement of terrestrialsurfaces in indoor and outdoor environments. SI-100 series sensorsoutput an analog voltage that is directly proportional to theinfrared radiation balance of the target (surface or object thesensor is pointed at) and detector, where the radiation balancebetween target and detector is related to the temperaturedifference between the two. For more information visithttp://www.apogeeinstruments.com/infraredradiometer/