1,721,489 research outputs found
An oscillator circuit for dual-harmonic tracking of frequency and resistance in quartz resonator sensors
No full textAn oscillator circuit is proposed that simultaneously excites and tracks two harmonic resonances in a quartz crystal resonator sensor. The oscillator outputs two pairs of signals, related to the sensor series resonant frequency and motional resistance for the fundamental and the third harmonic, respectively. The circuit also provides compensation of the sensor parallel capacitance for increased accuracy. By probing the resonator with the superposition of two harmonic modes simultaneously, enhanced sensing capabilities can be advantageously achieved because a larger set of parameters can be measured with a single sensor and its response is tracked in real time. Experimental tests were first run with the developed oscillator connected to 5 MHz AT-cut crystals exposed to different liquid solutions, obtaining results in good agreement with the theory. Evidence of different dynamic responses at the fundamental and the third harmonic was obtained, possibly related to differences in acoustic penetration depth into the liquid. The oscillator was then tested with the sensor loaded by microdroplets of liquid solutions deposited by a piezoelectric microdispenser. The oscillator could detect and track the resulting time response of the sensor, outperforming measurement methods based on impedance analysis in terms of speed and resolution, and evidencing a complex combination of effects in the sensor transient response
Applied Structural and Mechanical Vibrations: Theory, Methods and Measuring Instrumentation
No full text
Design and fabrication of a novel MEMS thermoelectric generator
No full textAbstractA thermoelectric microgenerator based on a novel structure, in which the heat flowing in elements with different thermal resistances produces local temperature differences in the device, has been designed, fabricated in BESOI technology and experimentally characterized. The temperature differences in the microgenerator are converted into a voltage by means of the Seebeck effect exploiting planar thermocouples
A Multivariable Motion Sensor Embedding an Improved Velocity Estimation Algorithm
No full textA multivariable motion sensor is presented that embeds into its onboard microcontroller a tailored algorithm, referred to here as the double-path (DP) algorithm, which estimates velocity in real time from position and acceleration signals simultaneously measured by the sensor itself. The multivariable motion sensor consists of a contactless magnetic linear position digital sensor and a triaxial digital accelerometer. The proposed algorithm estimates velocity by suitably mixing the integration of the acceleration and the linear fitting of the position, and it can operate under both trapezoidal and S-curve motion profiles. The velocity estimation accuracy has been assessed through simulations and experimental tests, which involved performance evaluation and a comparative analysis between the proposed algorithm and a Kalman filter (KF) both embedded into the sensor microcontroller. The experimental results are obtained by operating the sensor with a reference trapezoidal motion profile with a maximum velocity of 50 mm/s. The two root-mean-square estimation errors calculated for the sensor moving at constant acceleration and velocity are 1.32% and 0.58% of the maximum velocity, respectively
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