Characterization of a New Heat Dissipation Matric Potential Sensor

Luzius Matile,Daniel Wächter,Rolf Krebs,Roman Berger

doi:10.3390/s130101137

Luzius Matile, Daniel Wächter + Show 2 more

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https://doi.org/10.3390/s130101137

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Abstract

Soil moisture sensors can help to reduce the amount of water needed for irrigation. In this paper we describe the PlantCare soil moisture sensor as a new type of heat dissipation sensor, its calibration and the correction for temperature changes. With the PlantCare sensor it is possible to measure the matric potential indirectly to monitor or control irrigation. This sensor is based on thermal properties of a synthetic felt. After a defined heating phase the cooling time to a threshold temperature is a function of the water content in the synthetic felt. The water content in this porous matrix is controlled by the matric potential in the surrounding soil. Calibration measurements have shown that the sensor is most sensitive to −400 hPa and allows lower sensitivity measurements to −800 hPa. The disturbing effect of the temperature change during the measurement on the cooling time can be corrected by a linear function and the differences among sensors are minimized by a two point calibration.

Highlights

In many regions of the world water is scarce and the sustainable use of the water resources is indispensable
The matric potential can be measured directly by tensiometers [3] or indirectly by matric potential sensors that measure the water content of a porous matrix that is in equilibrium with the surrounding soil [4]
The purpose of this paper is the description of the PlantCare sensor as a new heat dissipation sensor, its calibration and the correction for temperature changes

Summary

Introduction

In many regions of the world water is scarce and the sustainable use of the water resources is indispensable. Water saving irrigation systems play a key role in the Sensors 2013, 13 sustainable use of water resources today and even more in future. The measurement of the soil moisture is of mayor importance for the controlling of irrigation systems. The matric potential can be measured directly by tensiometers [3] or indirectly by matric potential sensors that measure the water content of a porous matrix that is in equilibrium with the surrounding soil [4]. The indirect measurement of the matric potential has the following advantages: almost no maintenance and not so much limited at low matric potentials as tensiometers [5]

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