Pressure Correction in the Calibration of Heat Dissipation Sensors

<p>Heat dissipation sensors (HDSs) infer soil matric potential based on the measured rate of temperature rise from a heat source. The process for calibrating these sensors may use a pressure plate apparatus (PPA) to remove water to a certain calibration point that is controlled by pressure. Conventionally, the pressure within the PPA is released before the temperature change calibration points are measured (D<i>T</i>₀). This conventional HDS calibration approach can take several weeks. We propose that the equilibrated temperature change at pressure (D<i>T</i>_p) can be corrected empirically to the value at zero pressure. Based on measurements of 14 HDSs between 0.02 and 0.1 MPa, D<i>T</i>_p was on average 6.2% larger than D<i>T</i>₀. After pressure correction, using an empirical equation, the difference between the corrected D<i>T</i>_p and D<i>T</i>₀ was only 0.28%. These results demonstrate that this empirical approach provides sufficient accuracy to achieve HDS calibration without performing a PPA pressure release.</p>