Embedded processing of acquired ultrasonic waveforms for online monitoring of fast chemical reactions in aqueous solutions

摘要

Online ultrasonic monitoring of aqueous solutions involves acquisition of an ultrasonic waveform either propagated through the solution or reflected from a reflector placed inside it. Most conventional ultrasonic instruments upload the waveform to a separate computer which calculates from this waveform, e.g., the propagation delay and the attenuation coefficient. This approach limits the achievable update rate and requires use of a computer in addition to the ultrasonic instrument itself. This development utilizes embedded processing of the acquired waveforms in the ultrasonic instrument using a softcore MicroBlaze processor as a part of the overall FPGA design. A dedicated averaging subsystem (to reduce noise) and interleaved sampling subsystem (to achieve the equivalent sampling frequency of 1 GHz using a 50 MHz-clocked ADC) operate alongside each other, and are controlled by the MicroBlaze. After the completion of the waveform acquisition the MicroBlaze implements zero crossing algorithm to extract the sought after propagation delay. The instrument was applied for monitoring of neutralization reactions with the update rate of 5 measurements (i.e. acquiring and processing a full interleaved waveform then reporting the ultrasound propagation time) per second.