Precise Resonance Frequency Tracking Based on a DSP-Implemented Virtual Vector Voltmeter

Maintaining the resonance frequency of high-power ultrasound transducers is essential for applications such as sonochemistry, acoustic levitation and acousto-optic manipulation. This work presents a method to achieve resonance frequency tracking using a digital signal processor (DSP) implemented virtual vector voltmeter (VVV) for accurate phase detection. The system integrates three subsystems: a DSP for signal generation and phase detection, a microcontroller for control algorithms, and a custom PCB for signal amplification and measurement. Phase detection accuracy was evaluated over target phases from -5° to +5° using two bolt-clamped Langevin transducers with resonant frequencies of 28 kHz and 40 kHz, respectively. A 50-minute long-term performance test with the 40 kHz transducer showed phase tracking errors within ±0.35°, with maximum phase measurement uncertainties of ±0.0229° at 28 kHz and ±0.0213° at 40 kHz. These results demonstrate the DSP-implemented VVV’s ability to maintain precise phase tracking and resonance frequency adjustment, ensuring optimal performance in various ultrasound applications.