Resonating sensor for high-pressure and high-temperature environments

Sensor comprising a double-ended tuning-fork (DETF) sensing element 12 with piezoelectric resonator 20, optionally formed of Langasite or Langatate, formed with a slot 32 between tines 26, 28 that varies in width along the length of the tines. The tines may be symmetrical and may bow inwards (figure 5) or outwards (figure 6). The sensing element 12 may be encased by caps (14, 16, figure 1) which may be formed of the same materials as the sensing element. The sensor may be a pressure sensor. Temperature may be also be measured via a resistance detector or a second piezoelectric resonator with a pair of beams 76 figure 11 may be provided to measure temperature variation by forming acoustic standing waves. A method of measuring pressure using a DETF sensor and compensating for the measured temperature is also claimed.