Will our strain gauge accurately measure small forces on a baseball?

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Discussion Overview

The discussion revolves around the measurement of small forces on a baseball using a strain gauge attached to a cantilever beam setup. Participants are concerned about the sensitivity of the strain gauge in relation to the expected small forces (less than 3.5 ounces) and the potential deflection of the beam.

Discussion Character

  • Exploratory, Technical explanation, Debate/contested, Experimental/applied

Main Points Raised

  • One participant describes their experimental setup involving a baseball, a motor, and a cantilever beam with a strain gauge, expressing concern about measuring small forces.
  • Another participant suggests checking the sensitivity indicated on the strain gauge's data sheet and proposes using a more flexible support arm if necessary.
  • A different participant raises concerns about using a plastic arm due to the weight of the motor potentially causing bending in the beam.
  • There is a suggestion that metals provide more reliable strain gauge readings and a recommendation to use a thinner rod for better sensitivity.
  • One participant emphasizes that the choice of strain gauge depends on the specific application and that not all gauges are suitable for every situation.
  • Another participant advises consulting with a technician or someone experienced in planning experiments for guidance on strain gauge selection.
  • It is noted that while there are strain gauges capable of accurately measuring small deflections, they may be expensive, and participants suggest reviewing available options and designing the experiment accordingly.
  • Lastly, a participant recommends contacting the manufacturer for advice on selecting the appropriate strain gauge for their needs.

Areas of Agreement / Disagreement

Participants express various viewpoints on the type of strain gauge to use and the materials for the support arm, indicating that there is no consensus on the best approach. The discussion remains unresolved regarding the optimal solution for measuring small forces accurately.

Contextual Notes

Participants mention the importance of the strain gauge's sensitivity and the potential impact of the motor's weight on the beam's deflection, highlighting the need for careful consideration of materials and gauge specifications.

CanoIsDbo
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Hi, my group and I are doing an experiment on forces experienced on a baseball. Our setup involves the baseball attached to a motor, which is coupled to a cantilever beam (1/2 inch thick, 7 inch long aluminum rod). The beam has a strain gauge attached to it and we are recording data with labView. Our concern is with the sensitivity of the strain gauge. We don't believe we are going to get any forces greater then 3.5 ounces on the beam. Will the strain gauge measure the very very small deflection from such small forces?
 
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I would expect that the data sheet for the device should indicate the sensitivity. If it doesn't register what you want, could you go with a more flexible support arm?
 
Yes, we were thinking of possibly going with a plexiglass arm or some other type of plastic. Our concern with that is the weight of the motor (2 pounds) causing the beam to bend.
 
Plastic is probably a bad idea. Metals give more reliable strain gauge readings, go for a thinner rod.
 
It depends entirely on the gauge being used. You don't just grab one off the shelf and use it. A gauge is "sized" for the application.
 
Good point, Fred. I didn't think of that.
 
So, any recommendations of what type of strain gauge I need, sensitivity wise?

Thanks
 
Depends on your expected deflection and how accurate you need to be. I'd ask a technician, or if you have someone how oversees and plans experiments ask them. Failing that you'll have to do some donkey work and read through strain gauge data sheets.

Its not something we can really answer properly because you'll defintely be able to get strain gauges that can read deflections in the 1/2 inch bar very accurately, they could be very expensive. Best bet is to look at what strain gauges are available to you, and design your experiement to fit them.
 
And when in doubt, ask the manufacturer. They should be more than happy to advise you as to what unit will best suit your needs.
 

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