Usually, the situation should be avoided that the resonant frequency of crystal changes with temperature. However because the precision of the crystal resonance frequency is quite high, the temperature measurement can be realized by utilizing the relation between the resonant frequency and temperature. Its principle, measuring method are discussed and the experimental results are demonstrated in this paper.
Wenxiang Chen, Wenxiang Chen,
"Wireless temperature measurement utilizing the temperature-frequency character of crystal", Proc. SPIE 4710, Thermosense XXIV, (15 March 2002); doi: 10.1117/12.459627; https://doi.org/10.1117/12.459627