ABSTRACT
A thermocouple is generally used for determination of temperature. Its principle of operation is based on the fact that the voltage drop across dissimilar metals, which are placed in contact, is a function of temperature. Soil moisture content is measured using the time domain reflectometry (TDR) technique, which is based on the change in dielectric constant of a material with a change in moisture content. The horizontal strain in an asphalt or concrete pavement layer is determined on the basis of change in resistance of a body due to its elongation or shortening. The elongation or shortening is caused by stresses coming from the traffic load. Multidepth deflectometer (MDD) is used to determine the deflection of the different layers in the pavement under traffic loading. The instrument consists of a series of linear variable deformation transducers (LVDTs) at different depths stringed on a column that is inserted through a hole in the pavement.
