Capacitative electrode for measuring water content of plants - has carefully controlled porosity and may be applied round stem of plant

摘要

Two electrodes may be used for measuring the water content of a living plant; they consist of bands approx. 10 mm. wide and they may be wrapped round the stem of the plant with their nearest edges approx. 10 mm apart. The electrode consist of insulated coils of copper wire. The wire is insulated with lacquer and is bent into sinusoidal waves. The turns of the wire are then embedded in silicone rubber which is permeable to water vapour. The degree of permeability is carefully chosen. The outside of the assembly is then coated with a film of Mylar (RTM). One of the coils is supplied with HF from a generator, and the signals from the other coil are amplified and rectified.