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Introduction to Sensors and Data Analysis (Fall 2018)

Lab #5 Mass Measurement Device with Cantilever beam

Mass measurement contest

Mass measurement cantilever

Figure 1: Diagram of cantilever with unknown mass in position 2 out of 3 total positions. Measure changes in the natural frequencies to determine mass of object.

In the mass measurement contest, you will use natural frequency shifts to determine the mass of an object. There are three locations you can mount the object as seen in Figure 1, where the object is mounted in position 2. The experimental procedure only involves measuring natural frequency with the mass mounted in different positions. You can create an engineering model as we will do with experimental results from Ghatkesar et al. 2007 [1], as described in section 2.

You can use the modal analysis in Ansys [2] and apply a point mass to get predicted changes in natural frequencies. This will create a table of values for your given cantilever for known masses for interpolation as described in section 3.

Rules of Contest

  1. The masses must not leave the lab

  2. You cannot mount other known masses to the cantilever

  3. You must report your uncertainty in your mass measurement to enter the competition

  4. You must report your serial number "TJM 01-TJM 12" to enter the competition

  5. You may use the following tools and software: strain gage or accelerometer (not both), calipers, Ansys, Labview, Python, Matlab, and Excel

Winners of the contest

There will be two sets of winners for the contest:

  1. Lab group with the most accurate mass measurement calculated with $A=|m_{reported}-m_{actual}|$

  2. Lab section with the most precise mass measurement calculated with $P=\sum_{i=1}^{N}(m_{reported}-m_{actual})^2$

Where $A$ is the accuracy, $P$ is the precision, $m_{reported}$ is the reported mass from your experiment, and $m_{actual}$ is the actual mass of the object, and $N$ is the total number of lab groups in a section. The group and section with smallest A and P, respectively will win prizes. The prizes are as such

  1. ** $100 cash prize** put into your student accounts ($50/group member for group of 2)

  2. Donuts/cookies brought to your lab section

Lab #5 report should include details of the following

  1. Your design of experiments

  2. Your measured results

  3. Your predicted results from Ansys

  4. Your final calibration process for measuring a mass based upon natural frequency changes

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