A low-power, low-cost soil-moisture sensor using dual-probe heat-pulse technique

Jorapur, Nikhil and Palaparthy, Vinay S and Sarik, Shahbaz and John, Jobish and Baghini, Maryam Shojaei and Ananthasuresh, GK (2015) A low-power, low-cost soil-moisture sensor using dual-probe heat-pulse technique. In: SENSORS AND ACTUATORS A-PHYSICAL, 233 . pp. 108-117.

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Abstract

This paper presents the development and testing of an integrated low-power and low-cost dual-probe heat-pulse (DPHP) soil-moisture sensor in view of the electrical power consumed and affordability in developing countries. A DPHP sensor has two probes: a heater and a temperature sensor probe spaced 3 mm apart from the heater probe. Supply voltage of 3.3V is given to the heater-coil having resistance of 33 Omega power consumption of 330 mW, which is among the lowest in this category of sensors. The heater probe is 40 mm long with 2 mm diameter and hence is stiff enough to be inserted into the soil. The parametric finite element simulation study was performed to ensure that the maximum temperature rise is between 1 degrees C and 5 degrees C for wet and dry soils, respectively. The discrepancy between the simulation and experiment is less than 3.2%. The sensor was validated with white clay and tested with red soil samples to detect volumetric water-content ranging from 0% to 30%. The sensor element is integrated with low-power electronics for amplifying the output from thermocouple sensor and TelosB mote for wireless communication. A 3.7V lithium ion battery with capacity of 1150 mAh is used to power the system. The battery is charged by a 6V and 300 mA solar cell array. Readings were taken in 30 min intervals. The life-time of DPHP sensor node is around 3.6 days. The sensor, encased in 30 mm x 20 mm x 10 mm sized box, and integrated with electronics was tested independently in two separate laboratories for validating as well as investigating the dependence of the measurement of soil-moisture on the density of the soil. The difference in the readings while repeating the experiments was found out to be less than 0.01%. Furthermore, the effect of ambient temperature on the measurement of soil-moisture is studied experimentally and computationally. (C) 2015 Elsevier B.V. All rights reserved.

Item Type:	Journal Article
Publication:	SENSORS AND ACTUATORS A-PHYSICAL
Publisher:	ELSEVIER SCIENCE SA
Additional Information:	Copy right for this article belongs to the ELSEVIER SCIENCE SA, PO BOX 564, 1001 LAUSANNE, SWITZERLAND
Keywords:	Low-power DPHP sensor; Soil density; System design; Wireless communication
Department/Centre:	Division of Mechanical Sciences > Mechanical Engineering Division of Interdisciplinary Sciences > Centre for Nano Science and Engineering
Date Deposited:	12 Nov 2015 05:09
Last Modified:	12 Nov 2015 05:09
URI:	http://eprints.iisc.ac.in/id/eprint/52730

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