Infrared

Infrared Electromagnetic wave length Infrared light has a range of wavelengths, just like visible light has. "Near infrared" light is closest in wavelength to visible light and "far infrared" is closer to the microwave region of the electromagnetic spectrum. Infrared light has a range of wavelengths, just like visible light has. "Near infrared" light is closest in wavelength to visible light and "far infrared" is closer to the microwave region of the electromagnetic spectrum. Far infrared waves are in the thermal band and can measure the temperature of an object. The range is centered on 3 micrometers in length Far infrared waves are in the thermal band and can measure the temperature of an object. The range is centered on 3 micrometers in length

Humans, at normal body temperature, radiate most strongly in the infrared at a wavelength of about 10 microns. (A micron is the term commonly used in astronomy for a micrometer or one millionth of a meter.) Humans, at normal body temperature, radiate most strongly in the infrared at a wavelength of about 10 microns. (A micron is the term commonly used in astronomy for a micrometer or one millionth of a meter.)

Landsat 7 satellite, Modis satellite, and Astor satellite record data about the amount of infrared light reflected or emitted from the Earth's surface. Landsat 7 satellite, Modis satellite, and Astor satellite record data about the amount of infrared light reflected or emitted from the Earth's surface. Using different bands the Satellite can calculate the temperature of the surface but only to within 1.5 degrees of the correct value. Using different bands the Satellite can calculate the temperature of the surface but only to within 1.5 degrees of the correct value.

Infrared Thermometer Infrared thermometor Infrared thermometor Infrared thermometor Infrared thermometor

Crop water stress index Cwsi Cwsi Cwsi Accurate measurement of the leaf to air temperature require that leaf temperature must be known to within about ±0.1°C. Accurate measurement of the leaf to air temperature require that leaf temperature must be known to within about ±0.1°C. That is why satellite data can not be used to directly measure the CWSI That is why satellite data can not be used to directly measure the CWSI

Infrared thermometers are filtered to allow only a specific waveband, about 8 to 14 microns, to be transmitted to the IRT detector. Infrared thermometers are filtered to allow only a specific waveband, about 8 to 14 microns, to be transmitted to the IRT detector. This transmitted energy (E) is converted to temperature (T) via the Stefan-Boltzman Law which states E=esT4, where e is the emissivity of the object and s is the Stefan-Boltzmann constant (5.68 x 10-8 Joules m-2 s-1 K-4). This transmitted energy (E) is converted to temperature (T) via the Stefan-Boltzman Law which states E=esT4, where e is the emissivity of the object and s is the Stefan-Boltzmann constant (5.68 x 10-8 Joules m-2 s-1 K-4). Emissivity is defined as the radiation efficiency of a surface as compared to an ideal "black body" emitter. The emissivity of plants is Emissivity is defined as the radiation efficiency of a surface as compared to an ideal "black body" emitter. The emissivity of plants is 0.98.

Calibration of Infrared sensor A water cone calibrator can be built using a a 2 L beaker filled with water and placed on a magnetic stirring hot plate. A water cone calibrator can be built using a a 2 L beaker filled with water and placed on a magnetic stirring hot plate. The water has to be stirred with a large stirring bar so that the vortex produced a deep cone shape on the surface, which increased the effective emissivity of the water which is The water has to be stirred with a large stirring bar so that the vortex produced a deep cone shape on the surface, which increased the effective emissivity of the water which is The water temperature is measured with thermocouples placed in the beaker. The water temperature is measured with thermocouples placed in the beaker. Change the thermostat on the heater and measure the temperature from the thermocouples and infrared sensor. Change the thermostat on the heater and measure the temperature from the thermocouples and infrared sensor.

Corrected Target Temperature = Apparent Target temperature – Error Corrected Target Temperature = Apparent Target temperature – Error Error=(0.25/P(sb))*[((Apparent Target Temperature - H(sb))^2 ) - K(sb) ] Error=(0.25/P(sb))*[((Apparent Target Temperature - H(sb))^2 ) - K(sb) ] Sb is the sensor body temperature. Sb is the sensor body temperature.

Where Where P(sb) = *SB *SB^2 P(sb) = *SB *SB^2 H(sb) = *SB e-3*SB^2 H(sb) = *SB e-3*SB^2 K(sb) = *SB *SB^2 K(sb) = *SB *SB^2

The sensor can be read by a Fluke Digital Thermometers The sensor can be read by a Fluke Digital Thermometers Or a Campbell data logger. Or a Campbell data logger. The Fluke digital thermometer measures and stores the target temperature and the body temperature. The Fluke digital thermometer measures and stores the target temperature and the body temperature. Down load the data and analysis in a excel spreadsheet. Down load the data and analysis in a excel spreadsheet.

The thermocouple areType K (Chromel- Alumel) The thermocouple areType K (Chromel- Alumel) Set the thermocouple type in the Fluke. Set the thermocouple type in the Fluke.

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