Microwave technique has been developed and applied extensively in industrial and medical fields during the last three decades. More recently, the technique is also applied in agricultural field. However, there is very little academic literature about the application of microwave sensors especially in agriculture field. This book provides a scientific methodology for the microwave sensors study, supplemental to the rigorous mathematical analysis, microwave measurement techniques and engineering software that most researchers currently use. The scientific methodology include 1) develop the data acquisition program using Agilent VEE software, 2) investigate the electromagnetic field at sensor aperture using MATLAB and FEMLAB GUI software, 3) develop a multi-variable empirical model for coaxial sensor, 4) introduce a fast and economical calibration procedure for the sensor. Hence, this book should be useful to the researchers who would like to understand the background for the coaxial sensor and as a guide line for the researcher who would like to further their study in microwave materials processing, electromagnetic modeling, and dielectric modeling for specific materials.