Pulse echo method and apparatus for measuring the moisture content of materials

An apparatus for determining the moisture content of a material by measuring the dielectric constant of the material in which a measuring conductor is disposed and which forms the dielectric of such a measuring conductor utilizing the time lapse between the application of a pulsed electrical signal to the measuring conductor and the return of the echo of the signal, which electrical signal has a pulse duration greater than the time lapse between signal start and return of the echo thereof, said apparatus including means for determining the time between signal start and the return of the echo thereof, comprising a signal generator connected to said measuring conductor for supplying said electrical signal thereto, a switching device also electrically connected to said measuring conductor for sensing the return of the echo in said measuring conductor

• a counter, connected by way of a gate circuit, to an independently operating oscillator having a frequency whose cycle has a duration which is smaller than the expected smallest increment between the signal start and the echo thereof by only a small multiple and also to said switching device via said gate circuit,
• said gate circuit being held open by said switching device during the time between signal start and return of the echo reflected from the end of the measuring conductor so as to permit passage of count pulses to said counter during the time between signal start and echo return,
• said counter being adapted to sum up the oscillations generated by the oscillator while the gate circuit is open,
• and an evaluation and indication device connected to said counter, said evaluation and indicating device indicating the result of the counting procedure only when at least a predetermined number of gate openings have occurred considered to provide a count result of sufficient resolution,
• and said evaluation and indication device being capable of converting the count result to a number value for the moisture content of the material.