Low-Cost Control and Measurement Circuit for the Implementation of Single Element Heat Dissipation Soil Water Matric Potential Sensor Based on a SnSe(2) Thermosensitive Resistor

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 [Formula: see text] has a high thermal coefficient, from [Formula: see text] C in the 20 to 25 [Formula: see text] C to [Formula: see text] C in the 20 to 25 [Formula: see text] C. The [Formula: see text] 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 [Formula: see text] mW when the resistor changes from [Formula: see text] to [Formula: see text]. When the gravimetric water content of the porous block changes from dry to saturated ([Formula: see text]), we measured a variation of [Formula: see text] in the thermosensitive resistor, which results in an end-point sensitivity of 130 m [Formula: see text] /%. The developed system can easily meet the standard requirement of measuring the gravimetric soil water content with a resolution of approximately [Formula: see text] , since the resistance is measured with a resolution of approximately [Formula: see text] , three orders of magnitude smaller than the sensitivity.