In Situ Correction of Probe Deflection for a Thermo-TDR Sensor Provides Accurate Determination of Soil Water Content.

The thermo-TDR sensor is used to measure soil thermal properties and soil water content. Heat pulse sensor probe spacing is a very important parameter needed to determine soil heat capacity and soil water content. TDR probe length is a key prameter for water content measurement. Probe deflections causing probe spacing changes can occur when a heat pulse sensor is placed in a field soil. If changes in probe spacing are not accounted for, there will be large errors in heat capacity values and in soil water content. The longer the probe is, the easier the probe will deflect. Limited by the heat pulse part, thermo-TDR sensor is not long enough to provide caacurate TDR measured water content. An in situ probe spacing correcting method is presented and tested. Results indicate that even if probe spacings change, the in situ probe spacing correcting method can be used to determine accurate values of soil heat capacity and soil water content.