Measurement of surface temperature is a crucial component of energy transfer. Accurate measurement of the leaf-to-air temperature gradient is essential to the determination of the transpiration rate and stomatal conductance in both single leaves and plant canopies. This gradient is often less than 1oC, which means that leaf temperature should be measured to within 0.2oC.
To achieve this accuracy, the Apogee Instruments precision Infra Red Radiometers measure two temperatures. The primary thermocouple is used to measure the sensor body temperature. The output follows fundamental physics of the Stefan-Boltzmann Law allowing for a version of the S-B equation to correct for the effect of sensor body temperature.
Specifications
Field of View: 2 options SI-111 22oC half angle and SI-121 18oC half angle
Power Supply Requirements: 2.5V Excitation
Accuracy:
-10 to 65°C = ± 0.20oC
-40 to 70°C = ± 0.50oC
Output:
Target surface: SI-111 - 60 μV per °C difference from sensor body
SI-121: 40 μV per °C difference from sensor body
Sensor Body: 0-2500mV
Datalogger Channels required: 1 x Differential Voltage & 1 x Single Ended Voltage
Operating Environment: -55 to 80°C; 0 to 100% RH (non-condensing); Water resistant, designed for continuous outdoor use
Response Time: Less than 1 second to changes in target temperature
