I discussed the ethics and risks of our project with my group this week. I also attended the ethics lecture and discussed the ethics and risks of other projects in the class. We investigated the risk of using ultrasonic sensors and found that if the transmitter is driven with a high enough frequency, people in the area could suffer from dizziness and nausea. The risk threshold is 20 kHz. If we drive the transmitter with low-level voltage, the frequency range for the ultrasonic waves emitted should never exceed 1 kHz.
I characterized the ultrasonic sensor by trying different inputs to the transmitter and observing how the receiver responded, going through the process step by step for each variation. I started the collection of acoustic data using the ultrasonic sensor on healthy ductwork. We have not received our ADC yet, so I only attempted to characterize the use of our sensor on our specific duct material. Basically, I drove the transmitter and collected the output voltage range from the receiver using a voltmeter. This is not a fully detailed waveform that I can input into the processing code I have. I used one piece of duct (out of the 25 we collected) and took in total six measurements every 5 cm (the duct is about 15 cm long). I drove the transmitter with 3V, 5V, and 9V. The voltage limit for testing was 9 volts, which is the same limit provided by our current hardware design. I took two measurements for each input voltage because this seemed enough; after two, the voltage values became very repetitive without much variation. The data collection is documented in the file linked below.
The transmitter is hooked up to the battery and the receiver is positioned next to it to collect the echo of the signal. The prongs for the sensors seem slightly too long for this breadboard so the signal is unstable. For a proper, reliable connection, I may have to redesign this system. An image of the current setup is in the file linked below.
I also used an AD3 explorer to look at the waveform captured by the ultrasonic sensor. From using this software, I was able to obtain preliminary values such as frequency and peak-to-peak voltage. An example of the image is in the file linked below.
This is my work for this week: https://docs.google.com/spreadsheets/d/17F5QZGwymYqmGGup4V3u2_v8MdibjNQDQthjUrzVp3I/edit?gid=0#gid=0