Low-Cost Control and Measurement Circuit for the Implementation of Single Element Heat Dissipation Soil Water Matric Potential Sensor Based on a SnSe2 Thermosensitive Resistor

Abstract

A low-cost signal processing circuit developed to measure and drive a heat dissipation soil matric potential sensor based on a single thermosensitive resistor is demonstrated. The SnSe2 has a high thermal coefficient, from −2.4Ω/∘C in the 20 to 25 ∘C to −1.07Ω/∘C in the 20 to 25 ∘C. The SnSe2 thermosensitive resistor is encapsulated with a porous gypsum block and is used as both the heating and temperature sensing element. To control the power dissipated on the thermosensitive resistor and keep it constant during the heat pulse, a mixed analogue/digital circuit is used. The developed control circuit is able to maintain the dissipated power at 327.98±0.3% mW when the resistor changes from 94.96Ω to 86.23Ω. When the gravimetric water content of the porous block changes from dry to saturated (θw=36.7%), we measured a variation of 4.77Ω in the thermosensitive resistor, which results in an end-point sensitivity of 130 mΩ/%. The developed system can easily meet the standard requirement of measuring the gravimetric soil water content with a resolution of approximately Δθw=1%, since the resistance is measured with a resolution of approximately μ31μΩ, three orders of magnitude smaller than the sensitivity.

Continuous and Real-Time Measurement of Plant Water Potential Using an AAO-Based Capacitive Humidity Sensor for Irrigation Control

“…The water potential determines the movement direction of water molecules depending on how much water can be contained in the target sample or environment. For measuring the water potential information, there has been developed several methods such as psychrometric, 23 tensiometry, 24 heat dissipation resistive, 25 and capacitive. 26,27 However, most sensors were developed to target soil water potential.…”

DENSE: DiElectric Novel Soil Evaluation System to Electrochemically Profile Soil Matrices

“…Current state of sensors to track different soil properties including soil moisture have a gap between theoretical testing/modelling, lablevel analysis and complex instrumentation requirement for fieldlevel surveys. [26][27][28][29][30][31] Thus, in this study for the first time with direct applicability in a real-world setting, we probed this soil-water diffuse double layer to leverage the charge storage/retention vs the ability to transfer the charge by increasing or decreasing water (electrolyte concentration) content. In addition to that, it is also possible to track modulations the thickness of DDL and hence the mobility of cations within them to experimentally comment on variations with soil type.…”