@bachelorsthesis{1994G,
  title={Ultrasonic ranging in the undergraduate laboratory},
  author={Scott Goodchild},
  month={April},
  year={1994},
  abstract={There are many experiments in an undergraduate mechanics lab where
a compact ranging system can be of great benefit. The Ultrasonic Ranging
System (URS) developed by Polaroid  to automatically focus cameras is
ideally suited to such applications. The system is composed of an
electrostatic transducer, which acts as both transmitter and receiver,
and a single electronic module containing the drive, receiving, and
processing circuitry. To determine the distance to an object, the interval
time between the transmitted ultrasonic pulse and the received echo from
the object is measured With an appropriate clock rate, a resolution of
approximately 1mm can be obtained. 
A system of distance measurements based on a Polaroid URS
interfaced to an IBM PC-compatible computer is developed. The control
software makes it easy to perform a variety of measurements in the
undergraduate Mechanics lab.  Several sample experiments are described
to demonstrate the potential use of the device.},
  note={Supervised by E. Sternin}
}