ISSN:
1040-0397
Keywords:
Water sensor
;
Soil
;
Moisture
;
Modified electrode
;
Chemistry
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
Small inexpensive soil water sensors and the necessary electronics package for fast voltammetry (l04 V/s scan rate) are described. The sensor consists of a blunt ended hypodermic needle cathode containing a concentric PTFE insulating tube and therein, a Pt-wire anode. The sensing film is formed by dip-coating a 1:7 blend of a perfluorosulfonate and a polyestersulfonate polymer 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 sheathed in a PTFE tube that protrudes beyond the sensor tip and the protrusion gap is filled with a paste of talc and BaSO4 which serves as a water conduit between the soil and the sensor proper. The sensor is capable of making reliable moisture measurements between the wilting point and the field capacity of the soil sample; the response behavior consists of the combination of two nearly linear segments, the sensor output increasing steeply between the wilting point and ca. 60% of the field capacity and then much more gradually to the field capacity. The sensors have been field tested. No effect on sensor performance is observed even after burial under soil for several months.
Additional Material:
11 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/elan.1140070705
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