Abstract
In this paper, we characterize and model a bidirectional front-end based on pseudo-floating gate amplifier (PFGA) for actuation and read-out of resonating sensors. The basic idea consists of swapping the power supply of the PFGA in order to change the directionality of the front-end. A detailed description of the system has been discussed in this paper and supported by simulations and measurement results. A prototype has been fabricated using discrete components and tested with a real transducer (Murata MA40S4) and a Butterworth Van Dyke (BvD) load, which has proved to be proved to be a well approximated model for resonant sensors. The bidirectional amplifier has been implemented with the integrated circuit CD4007UB, which is a commercial discrete component containing low leakage MOSFET. The values chosen for the BvD load are R b = 330 Ω , L m = 60 mH, C s = 450 pF, C E = 2 . 2 nF, which are approximately the same values of the lumped parameters reported in the data-sheet of the real sensor. This transducer is characterized by a nominal resonant frequency of 40 kHz. Measurement results show good fitting with the models developed in this work and the possibility to predict the sensor response by using the BvD load.
Highlights
Resonant sensors are based on a vibrating structure, which changes their resonant frequency depending on the variations of a particular physical quantity in the surrounding environment [1].The changing in the resonant frequency is due to variations of the stiffness or mass of the mechanical structure
The oscillation generated by the Butterworth Van Dyke (BvD) load is characterized by a frequency of 32.4 kHz, which is smaller than the resonant frequency of the real transducer
VCC2 is characterized by a greater drop voltage than the value expected (' V3 /10 = 0.5 V). This is probably due to the fact that the parasitic capacitance in the circuit increases the total capacitance at the node VRLC, which is greater than the only CE, modifying the voltage divider between CC2 and CE
Summary
Resonant sensors are based on a vibrating structure, which changes their resonant frequency depending on the variations of a particular physical quantity in the surrounding environment [1].The changing in the resonant frequency is due to variations of the stiffness or mass of the mechanical structure. Resonant sensors are based on a vibrating structure, which changes their resonant frequency depending on the variations of a particular physical quantity in the surrounding environment [1]. Resonant sensors have great potential for numerous applications such as ultrasound, medical, military and many others. This is due to the fact that they offer high accuracy, high resolution and low drift [2,3]. In many of these fields, these types of sensors can be used to measure pressure, acceleration, rotation, etc. The first method is in general time consuming because the reading operation is based on a sweep in frequency of the exciting source [7]; the second one is characterized by high power
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