Apogee Instruments Apps
Clear Sky Calculator 2.1
The Clear Sky Calculator is used to determinethe need for recalibration of radiation sensors. It is mostaccurate when used near solar noon in the summer months. Thecalculator estimates the intensity of solar radiation (either totalglobal shortwave radiation, measured by pyranometers, or globalphotosynthetic photon flux density, measured by quantum sensors)incident on a horizontal surface at any time of the day, at anylocation in the world. The equations used to estimate clear skysolar radiation with the Clear Sky Calculator come from the clearsky solar radiation model used to calculate net radiation in theASCE Standardized Reference Evapotranspiration Equation(http://www.kimberly.uidaho.edu/water/asceewri/index.html). Theonly input requirements to the calculator are site elevation,latitude, longitude, reference longitude, and air temperature andrelative humidity measurements or estimates. These data aretypically easy to obtain, making the Clear Sky Calculator a simplesolar radiation reference that can be used to estimate pyranometerand quantum sensor accuracy and determine the need forrecalibration.When used near solar noon over multiple clear, unpolluted daysduring spring and summer months, accuracy of the Clear SkyCalculator is estimated to be ± 4 % in all climates and locationsaround the world. As an example, modeled incoming shortwaveradiation (SWi) from the Clear Sky Calculator closely trackedmeasured SWi (data from a heated and ventilated Kipp & ZonenCM21 pyranometer) for a clear day (April 21, 2012) in Logan, Utah.The ratio of measured SWi to modeled SWi was between 1.00 and 1.05(0 % and 5 %) from 9 AM to 6 PM (solar zenith angles less than65°). The average ratio from two hours before solar noon to twohours after solar noon was 1.02 ± 0.01 (2 ± 1 %). (seehttp://www.apogeeinstruments.com/using-the-clear-sky-calculator/)A more detailed discussion of Clear Sky Calculator accuracy isgiven on the webpage(http://clearskycalculator.com/model_accuracy.htm), where thenecessary accuracy of the required inputs is discussed.Apogee strongly encourages our customers to use the Clear SkyCalculator as an effective way to monitor pyranometer and quantumsensor performance and determine the need for sensor recalibration.If a sensor is consistently different from the Clear Sky Calculatorby more than a few percent, please contact us aboutrecalibration.
Field of View Calculator 1.1
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/
Field of View Calculator 1.1
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/
Light Unit Converter 1.2
The Light Unit Converter app from Apogee Instruments calculatestheconversions between different light units for various lightsourcesincluding T5 Sylvania fluorescent lights, metal halide,highpressure sodium, and sunlight. Units include shortwaveradiation(SW), photosynthetic photon flux (PPF, PPFD), Lux (lx)andFoot-candles (fc, lm/ft2, or ft-c). Definitions:ShortwaveRadiation - Shortwave radiation (SW) is radiant energywithwavelengths in the visible (VIS), near-ultraviolet (UV),andnear-infrared (NIR) spectra. There is no standard cut-off forthenear-infrared range; therefore, the shortwave radiation rangeisalso variously defined. It may be broadly defined to includeallradiation with a wavelength between 0.1μm and 5.0μm ornarrowlydefined so as to include only radiation between 0.2μm and3.0μm.There is little radiation flux (in terms of W/m²) to theEarth'ssurface below 0.2μm or above 3.0μm, although photon fluxremainssignificant as far as 6.0μm, compared to shorter wavelengthfluxes.UV-C radiation spans from 0.1μm to .28μm, UV-B from 0.28μmto0.315μm, UV-A from 0.315μm to 0.4μm, the visible spectrumfrom0.4μm to 0.7μm, and NIR arguably from 0.7μm to 5.0μm, beyondwhichthe infrared is thermal. Shortwave radiation is distinguishedfromlongwave radiation. Lux - The lux (symbol: lx) is the SI unitofilluminance and luminous emittance, measuring luminous fluxperunit area. It is equal to one lumen per square meter.Inphotometry, this is used as a measure of the intensity,asperceived by the human eye, of light that hits or passes throughasurface. It is analogous to the radiometric unit watts persquaremeter, but with the power at each wavelength weightedaccording tothe luminosity function, a standardized model of humanvisualbrightness perception. Photosynthetic Photon Flux -PhotosyntheticPhoton Flux (PPF), also known as PhotosyntheticPhoton Flux Density(PPFD) or Photosynthetically Active Radiation(PAR), designates thespectral range (wave band) of solar radiationfrom 400 to 700nanometers that photosynthetic organisms are able touse in theprocess of photosynthesis. PAR measurement is used inagriculture,forestry and oceanography. One of the requirements forproductivefarmland is adequate PAR, so PAR is used to evaluateagriculturalinvestment potential. PAR sensors stationed at variouslevels ofthe forest canopy measure the pattern of PAR availabilityandutilization. PAR is normally quantified as µmol photons/m2/s,whichis a measure of the photosynthetic photon flux (area) density,orPPFD. PAR can also be expressed in energy units (irradiance,W/m2);this is relevant in energy-balance considerationsforphotosynthetic organisms. Because photosynthesis is aquantumprocess, PPFD is generally used by plant biologists.Foot-candle -A foot-candle (sometimes foot candle; abbreviated fc,lm/ft2, orsometimes ft-c) is a non-SI unit of illuminance or lightintensitywidely used in the United States in photography, film,television,conservation lighting, greenhouse horticulture, thelightingindustry, construction-related engineering and in buildingcodes.The name "footcandle" conveys "the illuminance cast on asurface bya one-candela source one foot away". The unit is definedas theamount of illumination the inside surface of aone-foot-radiussphere would be receiving if there were a uniformpoint source ofone candela in the exact center of the sphere.Alternatively, itcan be defined as the illuminance on a one-squarefoot surface ofwhich there is a uniformly distributed flux of onelumen. Thus onefoot-candle is equal to one lumen per square foot orapproximately10.764 lux. In practical applications, as whenmeasuring roomillumination, it is very difficult to measureilluminance moreaccurately than ±10%, and for many purposes it isquite sufficientto think of one footcandle as about ten lux as istypically done inthe lighting industry.
