NDLI: An Automatic Soil Pore-Water Salinity Sensor Based on a Wetting-Front Detector

Content Provider	IEEE Xplore Digital Library
Author	Skinner, A.J. Lambert, M.F.
Copyright Year	2001
Abstract	The recent development of wetting-front detectors has provided a low-energy method of collecting transient samples of soil water under irrigation and rainfall conditions. A simple four-electrode conductivity sensor is presented for the automatic logging of soil water salinity extracted from the wetting front during that part of the irrigation cycle when accumulated salts in a crop root-zone are being mobilized under gravitational flows. The conductance of the platinum-on-ceramic cell is measured with an ac square-wave driven by a pair of micropower operational amplifiers whose rectified ground current acts as the dc signal proportional to electrical conductivity (EC). A 1:200 current mirror reflects this signal into a simple charge-balance 16-b analog-to-digital converter (ADC) bridge formed by a single op-amp acting in conjunction with the internal comparator of a low-cost microcontroller. Similarly, the platinum temperature sensor on the conductivity cell forms an integral part of a second 16-b charge-balance ADC in conjunction with a 1-mA current source. No instrumentation amplifier is required. The temperature coefficients of both the saline solution and the sensor circuit are picked up in the calibration process to produce an accurate temperature-corrected EC digital output that can be collected automatically by a data logger via the SDI-12 environmental data bus. Field data for a two-month period are presented in comparison to an automated vacuum sampling system, with reasonable agreement.
Sponsorship	IEEE Sensors Council
Starting Page	245
Ending Page	254
Page Count	10
File Size	1292362
File Format	PDF
ISSN	1530437X
Volume Number	11
Issue Number	1
Language	English
Publisher	Institute of Electrical and Electronics Engineers, Inc. (IEEE)
Publisher Date	2011-01-01
Publisher Place	U.S.A.
Access Restriction	One Nation One Subscription (ONOS)
Rights Holder	Institute of Electrical and Electronics Engineers, Inc. (IEEE)
Subject Keyword	Operational amplifiers Temperature sensors Detectors Irrigation Crops Conductivity measurement Current measurement Electric variables measurement Soil measurements Mirrors wetting-front detector Analog-to-digital converter (ADC) electrical conductivity (EC) sensor platinum resistance temperature device (PRTD) soil salinity soil solution sampler
Content Type	Text
Resource Type	Article
Subject	Instrumentation Electrical and Electronic Engineering

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1	Ministry of Education (GoI), Department of Higher Education	Sanctioning Authority	https://www.education.gov.in/ict-initiatives
2	Indian Institute of Technology Kharagpur	Host Institute of the Project: The host institute of the project is responsible for providing infrastructure support and hosting the project	https://www.iitkgp.ac.in
3	National Digital Library of India Office, Indian Institute of Technology Kharagpur	The administrative and infrastructural headquarters of the project	Dr. B. Sutradhar bsutra@ndl.gov.in
4	Project PI / Joint PI	Principal Investigator and Joint Principal Investigators of the project	Dr. B. Sutradhar bsutra@ndl.gov.in Prof. Saswat Chakrabarti will be added soon
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