Premium
An improved sensor for precision detection of in situ stem water content using a frequency domain fringing capacitor
Author(s) -
Zhou Haiyang,
Sun Yurui,
Tyree Melvin T.,
Sheng Wenyi,
Cheng Qiang,
Xue Xuzhang,
Schumann Henrik,
Schulze Lammers Peter
Publication year - 2015
Publication title -
new phytologist
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.742
H-Index - 244
eISSN - 1469-8137
pISSN - 0028-646X
DOI - 10.1111/nph.13157
Subject(s) - reflectometry , capacitance , water content , capacitor , frequency domain , materials science , dielectric , gravimetric analysis , time domain , volume (thermodynamics) , capacitive sensing , analytical chemistry (journal) , optoelectronics , chemistry , electrical engineering , voltage , electrode , physics , mathematics , geology , mathematical analysis , computer science , engineering , chromatography , quantum mechanics , computer vision , geotechnical engineering , organic chemistry
Summary One role of stems is that of water storage. The water content of stems increases and decreases as xylem water potential increases and decreases, respectively. Hence, a nondestructive method to measure stem water content (St WC ) = (volume of water) : (volume of stem), could be useful in monitoring the drought stress status of plants. We introduce a frequency domain inner fringing capacitor‐sensor for measuring St WC which operates at 100 MH z frequency. The capacitor‐sensor consists of two wave guides (5‐mm‐wide braided metal) that snugly fit around the surface of a stem with a spacing of 4–5 mm between guides. Laboratory measurements on analog stems reveals that the DC signal output responds linearly to the relative dielectric constant of the analog stem, is most sensitive to water content between the waveguides to a depth of c . 3 mm from the stem surface, and calibrations based on the gravimetric water loss of excised stems of plants revealed a resolution in St WC of < ± 0.001 v/ v. The sensor performed very well on whole plants with a 100‐fold increased resolution compared with previous frequency domain and time domain reflectometry methods and, hence, may be very useful for future research requiring nondestructive measurements of whole plants.