ME 3057 Fall 2022
Experiment Design and Project Plan
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Due: December 5th, 2022
This project is an experiment planning exercise; students are to design, plan and present a
measurement project in a document that can be reviewed and understood by the client and that
can be successfully conducted by a technician (or team) hired by the client.
This is an individual project. Students may not share files, or explanations. Students may use the
information and diagrams in this assignment file, with attribution.
After biking across Hawkins for the 100th time to save the day, the kids decide they want to
quantify their cycling power output to improve their response time. Being this is the early 80’s,
there are no commercially available power meters on the market. They are going to have to use
the computers and resources available at the local Radio Shack. Suzie and Dustin’s idea, as shown
in Figure 1, is to use a force transducer to measure the torque being applied to the chain ring of
their bikes, condition the resulting signal, and acquire it using a data acquisition system which
will store the force transducer voltage data to 5.5” floppy disk (1.2 MB of storage). Later analysis
will determine the torque, crank speed, and power from the force voltage data.
Figure 1: Concept schematic of homemade bike power meter and acquisition system
You are working a summer job at the Radio Shack between semesters at the Georgia Institute of
Technology and have decided to help them with the instrumentation design. Based upon the
bikes they will be using you have come up with a preliminary design of the system, shown in
Figure 2, which will measure the total torque which results from the left, 𝐹𝐿, and right, 𝐹𝑅, pedal
forces on the cranks of lengths 𝑟𝑝. The applied torque can then be determined from a force
ME 3057 Fall 2022
transducer measure the force, 𝐹𝑇, being applied to the chain ring where it connects to the hub
at a distance, 𝑟𝑡. The crank speed, 𝜔, will be determined by post-processing the data as it is
anticipated that the torque data for one revolution will show two maximums like the sample data
shown in Figure 3. It is expected that the data will be collected at a known constant sampling
rate, so only the force transducer data will need to be stored to perform the analysis. The bike
specifications can be found in Table 1.
Figure 2: Preliminary design for torque measurements for bike power meter
ME 3057 Fall 2022
Figure 3: Anticipated form of torque versus time for one revolution
The kids have come up with a few requirements for the power meter which must be met by your
design and analysis (summarized in Table 2). The power meter must be able to measure a
maximum torque of 300 N∙m, a maximum crank speed of 150 RPM, and maximum power of 1000
Watts (note that these conditions may not occur at the same time). They want the uncertainty
at the maximum power requirement to be less than 5% the total value with 95.4% confidence.
The data acquisition should be sufficient so that it meets these requirements and can save at
least 1 hour of cycling data. After the ride, they would like the data to be analyzed to determine
the crank speed, torque, and power in 10 second segments and which can then be plot to show
their performance over the hour ride. They would also like you to outline a simple calibration
routine for the system that can be done without removing the system from the bike.
Looking at the Radio Shack inventory, you have found a few force transducers, data acquisition
systems, and signal conditioning circuits that might be suitable for your design, listed in Table 3.
However, you need to perform a design study to determine which combinations will meet the
kids requirements. For this study you are going to calculate the uncertainty of the power is mainly
due to your sensor, signal condition, and data acquisition system choices for the force transducer
(you can assume that uncertainty from the crank speed analysis is negligible). They would like
you to report the results of your study in a short paper and provide a table of your selections and
the anticipated limits of the system, an example of which is shown in Table 4.
Deliverables
ME 3057 Fall 2022
Your job is to create a report proposing a design of the power meter and acquisition system, as
well as the required analysis, that meets the requirements listed above. It will justify your design
decisions with preliminary calculations showing that the requirements are met and provides a
simple calibration routine so that the system can be checked on the bike. The report must:
• Give a summary of the problem in your own words and the deliverables the design will
• Determine the appropriate sensors, signal conditioning circuits, and data acquisition
systems to meet the design requirement.
• Propose an analysis method to determine the torque, crank speed, and power for 10
second intervals of the collected data.
• Give a range of expected maximum values for torque, power, crank speeds, the system
and analysis will be able to provide.
• Develop a test plan to calibrate the system while it is on the bike.
• Complete the required table of equipment choices and capabilities for the force sensor
signal path (Table 4) and provide relevant figures and equations used in your calculations
in the appendix.
Report Requirements
Your report text should be roughly 1 page in length, with a 2-page maximum. Equations, displays
and tables should be placed on separate pages. An ME 3057 cover sheet should be used. You may
wish to organize your reports in 4 parts, like this:
1) Introduction / Needs – Briefly explain the client’s problem, your approach for getting the
answer and any expectations you may have.
2) Methods / Instrumentation Plan – Briefly present a listing what instruments you will use
and any actions you must take to collect and convert data into forms you can use.
3) Analysis / Expectations – Briefly explain how you will process your data to provide the
information to meet the client’s requirements and to implement your system.
4) Conclusion / Explanation – Briefly summarize what outcomes the client can reasonably
expect and how your system meets their goals and requirements.
ME 3057 Fall 2022
Equation 1: Torque, 𝑇, as a function of force, 𝐹, and a radius, 𝑟:
Equation 2: Power, 𝑃, as a function of constant angular velocity, 𝜔, and a torque, 𝑇:
Equation 2: Data size conversions:
8 𝑏𝑖𝑡𝑠 = 1 𝑏𝑦𝑡𝑒
106𝑏𝑦𝑡𝑒𝑠 = 1 𝑚𝑒𝑔𝑎𝑏𝑦𝑡𝑒 = 1 𝑀𝐵
Table 1: Bike and computer specifications
Variable Symbol Value
Crank Length 𝑟𝑝 150 mm
Sensor Radius 𝑟𝑡 50 mm
Storage Memory 𝑀 1.2 MB
Table 2: Power meter requirements
Variable Symbol Value
Maximum Power 𝑃𝑚𝑎𝑥 1000 W
Uncertainty @ Maximum Power 𝑢𝑃,𝑚𝑎𝑥 50 W
Maximum Torque 𝑇𝑚𝑎𝑥 300 N∙m
Maximum Crank Speed 𝜔𝑚𝑎𝑥 150 RPM
Recoding Time 𝑡𝑚𝑎𝑥 1 hour
Table 3: Available component, signal conditioning, and data acquisition hardware
Component Name Specifications
Force Transducer FT-20 20 N/V Gain
FT-200 200 N/V Gain
FT-2000 2,000 N/V Gain
Data Acquisition DAQ-A 4-bit resolution, 500 Hz sampling rate, -5 to 5 V range
DAQ-B 8-bit resolution, 200 Hz sampling rate, -5 to 5 V range
DAQ-C 16-bit resolution, 200 Hz sampling rate, -5 to 5 V range
Operational Amplifier OA-10 10 V/V gain
OA-100 100 V/V gain
Low-pass Filter LPF-100 100 Hz cutoff
LPF-500 500 Hz cutoff
LPF-1000 1,000 Hz cutoff
ME 3057 Fall 2022
Table 4: Force measurement specifications
Component Name Specifications
Force Transducer ? ?
Operational Amplifier (if needed) ? ?
Low-pass Filter (if needed) ? ?
Data Acquisition ? ?
Measurement Symbol Units Value
Maximum Force 𝐹𝑚𝑎𝑥 N ?
Force Uncertainty 𝑢𝐹 N ?
Maximum Torque 𝑇𝑚𝑎𝑥 N∙m ?
Torque Uncertainty 𝑢𝑇 N ?
Maximum Crank Speed 𝜔𝑚𝑎𝑥 RPM ?
Maximum Power 𝑃𝑚𝑎𝑥 W ?
Uncertainty @ Maximum Power 𝑢𝑃,𝑚𝑎𝑥 W ?
Maximum Recoding Time 𝑡𝑚𝑎𝑥 hour ?
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