"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.