Resonant Drive Configuration
Acoustic wave generation within a solid-state sensor utilizes two distinct vibrational modes to measure multiple physical parameters simultaneously. The application of dual mode excitation allows a single crystal resonator to provide data on both the target variable and the internal temperature of the device. By tracking the frequency difference between these modes, the system can self-compensate for environmental changes without an external thermistor.
Multi-Parametric Sensing
Quartz and silicon resonators often exhibit different temperature coefficients for their various vibrational shapes. Using dual mode excitation, a circuit tracks a primary mode sensitive to mass loading or pressure alongside a secondary mode that primarily responds to thermal shifts. This technique provides a local temperature measurement at the exact location of the sensing event.
Errors caused by thermal gradients between the sensor and a remote thermometer are thus eliminated.
Crystal Orientation
Selection of the specific cut or crystal angle determines the behavior of the vibrating modes. Designers must ensure that the dual mode excitation does not lead to unwanted energy coupling between the frequencies. Such interference can degrade the stability of the primary signal or introduce jitter into the timing loop.
Performance is verified by measuring the frequency stability over a broad range of temperatures and pressures to confirm the independence of the two signals.
System Integration
Digital signal processors handle the extraction of information from the complex waveform. Correct implementation of dual mode excitation results in a sensor that maintains high accuracy in unstable environments.
