| Summary: | 碩士 === 國立清華大學 === 奈米工程與微系統研究所 === 104 === This work reports the realization of double ended tuning fork (DETF) resonant transducer and Pirani gauge on a single device through the use of TSMC 0.35μm CMOS process technology. Through the measurement of DETF resonator under different pressure, a dynamic range of 3Torr to 200Torr was obtained; a dynamic range of 0.06Torr to 4Torr for the Pirani gauge; and a total combined dynamic range of 0.06Torr to 200Torr. By the technique of data post-processing, this work was able to enhance the dynamic range to 0.02Torr to 400Torr. The most prominent feature of this work is the realization of two different pressure sensing mechanisms on a single device thus achieving a smaller device area while maintaining a large dynamic range.
Usually resonant type pressure sensors are operated as an oscillator. Although it has a high sensitivity, this type of sensor is susceptible to the effect of parasitic capacitance and it has higher power consumption; also through the output signal only the frequency can be obtained. In contrast, by using the Ring-down measurement strategy both the Q factor and resonant frequency can be acquired with the additional benefit of avoiding parasitic capacitance effect. Due to the nature of Ring-down, it has a relatively lower power consumption compared to oscillator; however, it has a lower sensitivity.
By applying a square wave voltage signal to the designed DETF resonator, the motional current from the resonator due to the Ring-down motion was successfully measured. The Q factor at various pressures was also successfully extracted from the Ring-down waveform.
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