A new type of temperature sensor is suggested, actuated by piezoelectricty generated by means of thermal expansion of suitable materials. A crystal of quartz, preloaded in a special frame, senses the effects of load changes due to the difference between the thermal expansion of the frame and that of the quartz itself. A fixed proportion exists between the difference of potential, measurable on the appropriate faces of the crystal, and the temperature of the sensor. The tests carried out in order to check the characteristics of the new device fully confirm this proportionality. The voltage output of the sensor has been found to be about 0.001 V/C°.