Ultrasonic Resonant Tracker
1) Schematic 2) Power (blue) & Phase Angle (pink) 3) Resonant mode frequency sweep 4) AD9833 (MSOP) breakout board
As a part of a larger project, the requirement to drive a 200 watt ultrasonic probe at it’s media-varying resonant frequency was realized. An Atmega8 was used to manage feed back and instruct an AD9833 DDS to output the correct frequency.
Two methods were used as resonant mode feedback, phase angle and current sense. The phase angle was measured by detecting and comparing zero crossing of the current and zero crossing of voltage waveforms. The current sense was a common low side sense fed into the ADC of the controller. Data was captured via rs232 and logged in excel.
The ultrasonic probe was CNC machined according to vibrational analysis performed with FEA. Theoretical simulation and experimental results matched within 1/2 of a Hz.