Dielectric soil moisture sensors are now widely used in both research and commercial applications. Temperature and salinity response of these sensors has been reported and shown to be dependent on sensor characteristics such as probe geometry and excitation frequency. Improvements have come about empirically rather than through a systematic analysis of sensor physics. We obtained a model to describe soil-sensor interaction and used it to optimize sensor design. The model was then used to predict temperature and salinity response of the probe. Results of the simulations were compared to measurements made on a range of soils.