A new microstripline-type moisture sensor for heavily wet tea leaves

This paper describes a new sensor for high moisture measurement in producing green tea. The sensor is based on the microwave transmission technique. It uses a microstripline, on which tea leaves under test are overlaid. A microwave signal at 3 GHz was transmitted along the line, and attenuation and phase shift of the wave were measured. The moisture content of the leaves was calculated by a new idea of using the ratio of two signals corresponding to the attenuation and the phase shift. The sensor measured a moisture content range from 155 to 320% on a dry basis.