Source : Webster's Revised Unabridged Dictionary (1913)

Thermograph \Ther"mo*graph\, n. [Thermo- + -graph.] (Physics)
   An instrument for automatically recording indications of the
   variation of temperature.

Source : WordNet®

thermograph
     n 1: medical instrument that uses an infrared camera to reveal
          temperature variations on the surface of the body
     2: a thermometer that records temperature variations on a graph
        as a function of time [syn: {thermometrograph}]