| This dissertation is concerned with magnetoelastic sensors and sensing systems, primarily focusing on sensor characterization and instrumentation.; The sensor behavior and sensing mechanism are examined by modeling the sensor as a longitudinally vibrating rectangular beam, the longitudinal vibration of which is described by the equation of motion. The resonance frequency of a magnetoelastic sensor is determined by the sensor's length, mass density, and elasticity. From the perspective of signals and systems, the sensor is modeled as a mass-spring-friction second order system. The system response to an applied excitation consists of a steady-state response due to the applied excitation and a transient response due to the system's initial conditions. Analysis of both responses can be used for system characterization. A time-windowed periodic excitation is discussed in detail because it provides an efficient means of steady-state response analysis as well as transient response analysis.; The idea of threshold-crossing counting has been electronically implemented by developing a microcontroller-based instrument.; The microcontroller-based device has been fabricated, tested, and applied to laboratory experiments including pH monitoring and E. coli detection. The circuit was first prototyped on a breadboard and then on a printed circuit board (PCB). After preliminary results were obtained with breadboard prototyping and PCB board prototyping, the circuit was packaged into a plastic box containing a multifunctional coil. (Abstract shortened by UMI.)... |
