Spring 2012
Laboratory #3: Digital Sampling of
Time-Dependent Signals
A data report
only is required for this laboratory. Please carefully follow the instructions
for data report
formats.
Additional Instructions
Before coming to the Lab class,
you are to perform the following calculation and BRING the required plot to
the lab. Graph (e.g., using Excel a sine wave with a frequency of 100 Hz,
showing 25 cycles (use a smooth line to show the sine wave). Then on the same
graph, over the same time range, plot a series of data points from a 100 Hz
sine wave, but use points at 5.2 milliseconds intervals. Then connect these
points with a smooth curve.
Questions
In addition to the information required in the lab manual, your report must
answer the following questions in the appropriate section:
- Consider a signal coming from
a sensor that measures velocity in a turbulent flow. In such flows, we
assume the velocity, u(t), can be written as
u(t)=U+u'(t), where U is the average velocity
and u' is the time-varying component. You have a flow where the velocity
signal varies between 1 V and 1.05 V, and it is estimated that most of the
turbulent fluctuations occur at frequencies less than 6 kHz. You want to
accurately record u'(t) with a data acquisition system very similar to the
one used in this lab. Assume that the computer system can sample at rates
of up to 150 kHz and can digitize the signal into 4096 levels (=212, or 12
"bits") between the following possible ranges: -10 to 10 mV,
-100 to 100 mV, or -10 to 10 V (note: the computer can only use ONE of
these ranges). How could you use the computer system, in conjunction with
the filter, to accurately record u'(t)?