Physics 171
Lab #1 (take-home)
Rain gauge design and construction
This take-home lab project will require you to use some imagination and ingenuity. You will be
constructing your own rain gauge which will then be used in later labs about precipitation rate
analysis and acid rain pollution.
It might seem trivial to measure the amount of rain that falls from the sky, but it actually
becomes a challenging problem if you try to make your measurement with precision and
accuracy. That will be our common goal. There are many reasonable and very different
solutions. I encourage you to come to office hours if you seem stuck.
Here are the requirements:
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Precision: The gauge must be able to measure rainfall with a resolution of at least 0.05
inches (For example .55” must be distinguishable from .60”). A resolution of 0.01 inches
is preferable and will attain a higher grade. This resolution will not be achieved with a
straight-walled can and a standard ruler marked in 1/16 inch increments. There are
many ways to accomplish an increase in resolution, but perhaps the simplest is to have a
wide-mouth opening for your gauge.
Accuracy: The rain gauge must be accurate. This should go without saying. Slight
random error based on meteorological conditions (side-blowing rain) is unavoidable, but
systematic errors of calibration must be eliminated.
Materials: The rain gauge should be durable enough to last through the semester outside.
Materials should be non-reactive (ideally plastic or glass) so that chemical composition is
unaffected. Material cost should be less than $20.00 and should in no way incorporate a
commercially available gauge. Every day materials such as bottles and kitchen
containers are possible components, but many local hardware stores carry useful and
inexpensive pieces as well.
Assignment:
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Design: A detailed sketch (hand or computer drawn) and one-page description of
materials and measurement technique will be due in class on Friday, Sept. 4.
Measurement technique description must be detailed and include a sample
calibration or unit conversion calculation.
Build: The gauge itself must be completely constructed by lab during the week after
midterm break where it will be tested outside. If it passes the test, it will be deployed for
the remainder of the semester and incorporated into several labs.