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USGS · 70024410

Calibration and temperature correction of heat dissipation matric potential sensors

A. L. Flint·G. S. Campbell·K. M. Ellett·C. Calissendorff
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Abstract

This paper describes how heat dissipation sensors, used to measure soil water matric potential, were analyzed to develop a normalized calibration equation and a temperature correction method. Inference of soil matric potential depends on a correlation between the variable thermal conductance of the sensor's porous ceramic and matric potential. Although this correlation varies among sensors, we demonstrate a normalizing procedure that produces a single calibration relationship. Using sensors from three sources and different calibration methods, the normalized calibration resulted in a mean absolute error of 23% over a matric potential range of −0.01 to −35 MPa. Because the thermal conductivity of variably saturated porous media is temperature dependent, a temperature correction is required for application of heat dissipation sensors in field soils. A temperature correction procedure is outlined that reduces temperature dependent errors by 10 times, which reduces the matric potential measurement errors by more than 30%. The temperature dependence is well described by a thermal conductivity model that allows for the correction of measurements at any temperature to measurements at the calibration temperature.

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A. L. Flint, G. S. Campbell, K. M. Ellett, C. Calissendorff. 2002. Calibration and temperature correction of heat dissipation matric potential sensors. https://doi.org/10.2136/sssaj2002.1439

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