Pressure Correction in the Calibration of Heat Dissipation Sensors

Journal Article · 22 November 2019 · Vadose Zone Journal

DOI: https://doi.org/10.2136/vzj2019.05.0052 · OSTI ID:1577978

Thomle, Jonathan N. ^[1]; Zhang, Z. Fred ^[1]; Dai, Gao L. ^[1]

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1. Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

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 (ΔT₀). This conventional HDS calibration approach can take several weeks. We propose that the equilibrated temperature change at pressure (ΔT_p) can be corrected empirically to the value at zero pressure. Based on measurements of 14 HDSs between 0.02 and 0.1 MPa, ΔT_p was on average 6.2% larger than ΔT₀. After pressure correction, using an empirical equation, the difference between the corrected ΔT_p and ΔT₀ was only 0.28%. These results demonstrate that this empirical approach provides sufficient accuracy to achieve HDS calibration without performing a PPA pressure release.

• Research Organization: Pacific Northwest National Laboratory (PNNL), Richland, WA (United States)
• Sponsoring Organization: USDOE
• Grant/Contract Number: AC05-76RL01830
• OSTI ID: 1577978
• Report Number(s): PNNL-SA-142103
• Journal Information: Vadose Zone Journal, Vol. 18, Issue 1; ISSN 1539-1663
• Publisher: Soil Science Society of AmericaCopyright Statement
• Country of Publication: United States
• Language: English