The HPF01 Self-Calibrating Heat Flux Sensor is intended for soil heat flux measurement applications requiring the highest possible degree of measurement accuracy. Employing an innovative pulsed heat self-calibration technology (via the Van den Bos-Hoeksema method), the HPF01 minimizes the possibility of sensitivity and temperature dependence induced error effects inherent in conventional soil heat flux sensor models resulting from varied soil moisture content and temperature.

The HPF01 Self-Calibrating Heat Flux Sensor is primarily intended for high accuracy heat flux measurement studies within the soil medium it is buried. The sensor incorporates a passive thermopile detector embedded within a thin ceramic plastic composite body, with an integrated thin film heating element mounted atop the sensors composite body. The HPF01 outputs a linear millivolt signal generated by the differential temperature across the sensors body and proportionate to the local soil heat flux. The heating element can be cycled on/off at user defined timing intervals to perform an in-soil calibration check, thus allowing the user to derive sensor calibration factors ideally matched to the soil conditions at the time of measurement; implicitly cable connection, data acquisition and data processing are also tested. For certain application environments, the user may wish to consider the installation of two HPF01 sensors; sensor redundancy offers the possibility of improved spatial averaging and QA of the processed measurement result.

Applications Agrometeorology (evapo-transpiration)

Specifications Sensitivity (nominal) 50 µV/Wm2 Resistance (nominal) 2 h Temperature Range -30 to +70° C Measurement Accuracy ±3% Film Heater Specifications Sensitivity (nominal) 50 µV/Wm2 Resistance (nominal) 100 h Voltage Input/Output 9 - 15 VDC / 0 - 2 VDC Duration of Calibration ±3 min. @ 1.5 Watts, typically every 3 - 6 hours Average Power Consumption 0.02 or 0.04 Watts