Digital phase-locked loop circuit for driving resonant sensors
Sprache des Titels:
Resonant mechanical sensors are powerful tools for measuring, e.g., physical properties of fluids. Suitable systems
for real-time monitoring of a sensor?s resonance behavior are, e.g., oscillator circuits and phase-locked-loop circuits.
In this contribution, we present a novel specific digital phase-locked-loop circuit with the ability to determine damping,
as well as resonance frequency, and providing automatic compensation of spurious parallel capacitances of the sensor.
Instead of a phase-frequency detector, the system measures phase and amplitude of the sensor signal with a 16-bit
ADC and uses this information to control a numerically-controlled oscillator. Due to the used 4-channel digital
synthesizer, the sensor can be excited with up to three frequencies at the same time facilitating enhanced performance
in terms of simultaneous measurement of higher order resonances and compensation of spurious capacitances.