Time Domain Reflectometry(TDR) Principle

  • TDR is one of the most recent technique for determining soil moisture and finding out its way to put forward on practical basis.
  • The technique involves transmitting Radio frequency wave through medium(guided line) and get it reflected.
  • The transit time between transmitted & reflected help us to determine velocity.
  • The velocity of RF wave depends on dielectric constant & losses within measuring system.


V is velocity attenuated due to dielectric losses and other losses.
c is speed of light.
ƺ depends on dielectric constant of medium.

  • Accurate up to upto 2%.