Overview of Status of Analysis, Design, Fabrication, Tests, etc.
Accomplishments from Previous Week
Selected a scale for the range which we wish to measure
0-100 grams
Monofilament tests range from 1-75 g, so this test will give us more data at the higher end of the scale than the monofilament can provide
Selected gain of 1800
Still needs justification and theory agreement and can be changed and tested very easily
Risk reduction completed determined that length was invariant on voltage output of the load cell
Tested various lengths and thicknesses for beams by static load testing and did FEA to show output is invariant
Mounted a prototype to have a more robust and rigid mechanism
Goals for Next Week (list names after each item). Use specific and measurable objectives.
Purchase LCD screen
Research tilt sensors to correct orientation issues
Solidify the prototype
Decide on mechanical stopping mechanism and if we want to implement it
Begin designing chassis for load cell
Sponsor Comments from Last Meeting and Actions Taken to Address these Comments (indicate date of comments and if via email or in person)
4/16/2013
No meeting, general overview and updates provided through presentation email
Instructor Comments from Last Meeting and Actions Taken to Address these Comments (indicate date of comments and if via email or in person)
Meeting with Dr. Delson, 4/11/2013
Increase the voltage range from 2-V to 0-5 V to get more points and make readings finer
Met with Steve Roberts to understand reference voltage. Will implement 9-12 V source to power the op amp and sensor so the points can be defined in a much larger range
Linearity, accuracy, hysteresis, resolution, repeatability
Linearity and repeatability: did static load tests to find linearity for different lengths and widths
Hysteresis: During linearity tests, worked backwards and removed loads in the same order as applied to find very to little to no hysteresis for the scale
This may change because we have to look at fatigue of material
Resolution: meeting with Steve Roberts will be implemented soon
Maximum load: 300g
Reduced to 100g after discussing with sponsor to exceed monofilament capabilities, yet providing beneficial information
Length of moment material
Sensor is length invariant due to the shape of a binocular load cell and Mc/I does not apply to this configuration
Adjust for tilt with accelerometer
Correspondence with sponsor says it does not need to be used parallel to the floor
Obtain Arduino with higher resolution (~4000 bits)
May not be necessary due to electrical manipulation that will be tested
Shim stock piece to act as a spring
Comments from Other Students in the Class (indicate date of comments and if via email or in person)
None
Risks and Areas of Concern
Determining if more resolution is needed after testing current load cell with existing microcontroller setup in clinical conditions
Does the system need more flexibility to increase ease of low-range testing?
Determine the travel distance with new shim stock
Schedule
Working on outer casing/chassis system for the sensor. Gear our design toward form factor and ease of use.
Solidify electrical components and their impedance values.
Update Gantt chart.
Budget (list amount spent and amount remaining)
No other purchases from last update
Budget remaining: $1414.41