Force Gauge vs. Scale: Which is a More Accurate Measure of Deformation?

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Discussion Overview

The discussion revolves around the comparison between using a digital force gauge and a scale to measure the force required to deform various items. Participants explore the implications of using each device in terms of accuracy and the nature of the measurements taken during deformation.

Discussion Character

  • Debate/contested
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • One participant questions the difference in measurement accuracy between a digital force gauge and a scale, noting the cost disparity.
  • Another participant points out that not all scales are well calibrated and may exhibit hysteresis, which could affect measurement accuracy.
  • A participant suggests that scales might give different readings based on the energy absorption characteristics of the object being compressed, using examples of a wall versus a pillow.
  • In response, another participant argues that the scale records the actual force applied, regardless of the object's compressibility, emphasizing that the force applied cannot exceed the force the object exerts back.
  • Another participant clarifies that using a force transducer measures the force transmitted through the object rather than the force of the punch itself, highlighting the role of mass and acceleration in the measurement.

Areas of Agreement / Disagreement

Participants express differing views on the accuracy and nature of measurements taken by scales versus force gauges. There is no consensus on which method is superior, and the discussion remains unresolved regarding the implications of energy absorption and calibration issues.

Contextual Notes

Participants acknowledge potential limitations in the calibration of scales and the effects of hysteresis, but these factors are not fully resolved within the discussion.

momotime
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I'm trying to make a fixture measure how much force it takes to deform various items.

However, digital force gauges costs upwards from while simple scales don't cost much at all. What's the difference between using a fancy force gauge and placing a digital scale underneath an item that's being compressed?

Thanks!
 
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Nothing I can think of.

Edit: Except that not all cheap weighing scales are well calibrated. Some may also have hysteresis (eg you get a different result when the force is increasing vs decreasing). Presumably you aren't planning to send the experiment to another planet or up a mountain (eg no changes in g?)
 
Thanks for the input! I think I figured it out though... I'm assuming scales can give a different reading from a force gauge because items can absorb energy, making the scale give a different reading than the force being acted upon the object?

Example -- if you use a scale to punch a wall, the maximum reading will reveal the force of your punch. But if you use a scale to punch a pillow, the absorption of force will cause the reading to change...?
 
momotime said:
Example -- if you use a scale to punch a wall, the maximum reading will reveal the force of your punch. But if you use a scale to punch a pillow, the absorption of force will cause the reading to change...?

No - in both cases the scale is correctly recording the force that you're actually applying.

It takes much less force to compress a pillow than it does to compress a wall - and you cannot push on an object any harder than it pushes back on you.
 
What Nugatory said, plus, if you are putting a force transducer underneath the object, as in your OP, you are not measuring "the force of your punch." You are measuring the force that is transmitted through the object and reacted against whatever it is resting on. The difference is the mass x acceleration of the object, if it changes shape when you punch it.
 

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