Hmm, I'm going to need to get to more like .1mm or better for my application. The reason I thought this might be feasible (and I could just be missing some simple factor that I'm not aware of, like variable response time in the crystal or something) is that I want to send the data to a processor and actually figure out where the peak is--so the idea rests around having a high speed analog reading of the pulse from the transmitting transducer. Is this possible? What I'm basically looking for I guess is a high speed oscilloscope circuit or chip that can read these values and then get them to my arduino.