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Resonant temperature sensors have draw n considerable attention for their advantages such as high sensitivity,digitized signal output and high precision. This paper presents a new type of resonant temperature sensor,w hich uses capacitive micromachined ultrasonic transducer( CM UT) as the sensing element. A lumped electro-mechanical-thermal model w as established to show its w orking principle for temperature measurement. The theoretical model explicitly explains the thermally induced changes in the resonant frequency of the CM UT. Then,the finite element method w as used to further investigate the sensing performance.The numerical results agree w ell w ith the established analytical model qualitatively. The numerical results show that the resonant frequency varies linearly w ith the temperature over the range of 20 ℃ to 140℃ at the first four vibrating modes. How ever,the first order vibrating mode show s a higher sensitivity than the other three higher modes. When w orking at the first order vibrating mode,the temperature coefficient of the resonance frequency( TCf) can reach as high as-1114. 3 ppm / ℃ at a bias voltage equal to 90% of the collapse voltage of the M CUT. The corresponding nonlinear error w as as low as 1. 18%. It is discovered that the sensing sensitivity is dependent on the applied bias voltages. A higher sensitivity can be achieved by increasing the bias voltages.
Resonant temperature sensors have draw n attention for their advantages such as high sensitivity, digitized signal output and high precision. This paper presents a new type of resonant temperature sensor, w hich using capacitive micromachined ultrasonic transducer (CM UT) as the sensing element. A lumped electro-mechanical-thermal model w as established to show its w orking principle for temperature measurement. The theoretical model explicitly explains the thermally induced changes in the resonant frequency of the CM UT. Then, the finite element method w as used to further investigate the sensing performance. These numerical results agree w ell w ith the established analytical model qualitatively. The numerical results show that the resonant frequency varies linearly w ith the temperature over the range of 20 ° C to 140 ° C at the first four vibrating modes. ever, the first order vibrating mode show sa higher sensitivity than the other three higher modes. When w orking at the The first order vibrating mode, the temperature coefficient of the resonance frequency (TCf) can reach as high as -1114. 3 ppm / ° C at a bias voltage equal to 90% of the collapse voltage of the M CUT. The corresponding nonlinear error w as As low as 1. 18%. It is discovered that the sensing sensitivity is dependent on the applied bias voltages. A higher sensitivity can be achieved by increasing the bias voltages.