Optimizing Temperature Corrections for VHF Dielectric Moisture Measurements

Abstract

Grain moisture meters are expected to provide accurate measurements over wide ranges of grain temperature as well as moisture. Considerable temperature effect data (for the most part, unpublished) exists for commercial dielectric grain moisture meters that operate in the 1 to 20 MHz frequency region, but very little information is available for the VHF frequency range. This research was performed to support the development of a new dielectric moisture measurement algorithm that uses a measurement frequency of 149 MHz. Instrumentation and test methods were developed to efficiently measure dielectric characteristics of grain samples over wide temperature ranges. Data were collected for a range of moisture levels for six grain types. Alternative forms of temperature correction functions were developed and evaluated. Optimum coefficients were derived for correcting moisture measurement error due to temperature differences. Limits were established for measuring moisture content for samples at temperatures below zero Celsius.