Dasgupta's voltammetric sensors : a type of Soil Water Content Sensors on the sowacs web pages


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			Dasgupta's voltammetric sensors how they work, some literature on them, where to get them and how much they cost:

photographs

Voltammetric sensor??

basic principles

STOP PRESS 19 June 03

New info has just come to light on this category of sensors.
The sowacs email discussion list is therefore working towards describing the sensor type for inclusion on this page... contibutions welsome.. start here (and then read the archives of emails since June 19 03)
A microfabricated amperometric moisture sensor Xiao-Li Su published 16 July 2001 in Talanta 56 (2002) 309-321 1996 See below for details from the sowacs archives...

advantages

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disadvantages

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general

I first read about it here (Cheap sensor HYPODERMIC)

manufacturers

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literature

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details

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other

Here follow the relevant contents extracted from the sowacs archive for convenience:

******** ******** Welcome to the second message of the Soil Water Content Sensor discussion group! ********** (SoWaCS group ) ************ V O L T A M M E T R I C S E N S O R S (NB: not volumetric!) ********** ************ 23 April 1996 Over and above the TDR discussion, this file details a new type of sensor that seems to have not yet been "discovered". I first read of it in the TWRI newsletters, and my inquisitiveness (and net surfing) finally paid off when the author sent me a copy of his paper: Huiliang Huang and Purnendu K Dasgupta. 1995. Fast voltametric sensors for the measurement of soil water activity. Electroanalysis 7:7 pp 626-632 I quote from the abstract:" The sensor consists of a blunt ended hypodermic needle cathode containing concentric PTFE insulating tube and therein, a Pt-wire anode. The sensing film is formed by dip-coating a 1:7 blend of a perflourosulfonate and a polyestersulfonate ploymer at the tip of the needle. Atop this sensing film is a composite protective film of cellulose acetate and nylon that inhibits the passage of ionic or low MW constituents and allows the transport of water.... The sensor is capable of making reliable moisture measurements between the wilting points and the field capacity of the soil sample: the response behaviour consists of the combination of two nearly linear segments, the sensor output increasing steeply between wilting point and ca. 60% of the FC and then much more gradually to the FC. The sensors have been field tested. No effect on sensor performance is observed even after burial under soil for several months." The paper itself gives some indication of the excellent prospects of the sensor: there is no hysteresis, and the repeatability appears excellent. According to Prof Dasgupta - there has been no attempt at commercialisation as yet, but only due to his time constraints. He urged me to publicise this point through this forum. (Companies take note!) Apparently the technology has not yet been well accepted by Agronomists, but there are numerous other applications where the technology could have good use. High humidity measurements (in the 95 to 100% area) are difficult any other way, yet this method appears to be able to be tweaked to cover this range well. A further use of the sensor has been reported but has more to do with the petrochemical and related industry: Anal. Chim. Acta, Amy E. Clough: Measuring water content of Synthetic Lubricants with polymer coated sensors, 315:15-26 (1995) Prof Dasgupta can be contacted at: Purnendu K. Dasgupta Department of Chemistry and Biochemistry Texas Tech University Lubbock, TX 79409-1061 Ph (806) 742-3064 Fax (806) 742-1289 END -.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-. Bruce Metelerkamp [whilst] SOIL WATER RESEARCH OFFICER Institute for Commercial Forestry Research, University of Natal, PO Box 100281 Scottsville, ZA3209 Rep. of South Africa Voice: 27 331 62314 E-mail:bruce@icfr.unp.ac.za FAX: 27 331 68905 URL http://www.icfrnet.unp.ac.za/~metele /SoWaCS.html /RR.html

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Campbell Scientific

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PRISM - CMP by Irrigation Scheduling Methods, Inc.

Research, Products, Consultancy on Real-Time Water Dynamics

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Capacitance (or FDR)
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18/06/2003