ADC based ultrasound spirometry measurement system design

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Dr. Kovácsházy Tamás
Department of Measurement and Information Systems

"Designing an ADC based ultrasonic spirometry system."

This thesis is about analyzing one type of ultrasonic spirometry measurement. In the first part I describe the basis of spiromery from the engineers and the medical point of view.

The second part of the paper is about the Thormed Ltd.'s currently used measurement system. I describe the measuring mechanics, analyze the faults and malfunction sources of the current configuration, and I attempt to reduce the impact of the problems.

As I was working for Thormed Ltd. I had an idea, instead of detecting the zero-cross we could improve the resolution of the measurement by measuring the magnitude of the signal. I describe the basis of analog-to-digital converters and compare them to the current system's comparator in the third part.

I've designed an ADC based system to validate my theory. Henceforward I describe the component selection, the printed circuit board design, the software, the emerging problems, and the solutions for them.

In the end I summarize the observations of the design and describe how to build a more accurate, well functioning measuring system comparable to the zero-cross detection based measurement.


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