Acoustic Time Domain Reflectometry

  • Simultaneously we have heard that Ultrasonic waves being used for level, flow, detection, but no it can be also used for temperature detection.

  • Principle of operation is very simple acoustic waves travels at different speeds at different temperatures.

  • Velocity of acoustic wave is high when temperature is low, and vice-verse.

  • Acoustic waves are passed through solids, and based on transit time we are able to determine temperature.

  • Temperature of various gases can be determined by triggering pulse and determining transit time.

  • Rhenium sensors provide better output in hostile environment.

  • They can measure temperature up to plasma level(20,000 C).

  • The acoustic pulses are generated by piezoelectric crystal, which resonate at frequency range of about 3Mhz.

Temperature and velocity exhibits relationship derived by the formula:

c is velocity of sound.

R is gas constant per mole.

k is Boltzmann constant.

m is mass of single molecule.

T is absolute temperature.


  • High accuracy

  • No leakage

  • Used where medium is at very high temperature.


  • High cost.

  • No ideal gas behaviour.

  • The device posses drift in parameters.


  • Furnace & Nuclear reactors.

Never heard of this technique.
:+1: Good effort