Minimum microstrains that a wheatstone bridge or strain gauges will pick up?

In summary, The speaker is trying to measure the torque output of a cyclist by measuring the shear force in the crank arms. They have calculated that the minimum amount of strain they need to pick up is 6e-6 m/m. They plan on using a full wheatstone bridge with a constant voltage supply and an amplifier. They are concerned about signal noise and temperature changes and are unsure about the accuracy they can achieve at this level of strain. They mention having experience with strain gauges and being able to detect changes of one or two microstrain with a very accurate voltmeter.
  • #1
Vale-46
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I'm wanting to measure the torque output of a cyclist by measuring the shear force induced in the crank arms.

I've done some calculations for the minimum amount of strain that I'll want to pick up and it is around 6e-6 m/m. I'll be using a full wheatstone bridge with a constant voltage supply (I'm not sure what is a decent voltage to use) which will be plugged into an amplifier of some sort I guess.

Signal noise and temperature changes will be an issue I guess, but I'm just wondering what sort of accuracy I ought to be able to get at this sort of strain level.

The equation for the constant velocity circuit is of no use to me as all I can end up with is a relationship between the change in current and the change in resistance, plus I don't know what sort of resolution for resistance change measurement I can get.
 
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  • #2
I worked with strain gauges some years ago and with a voltmeter that read accurately down to microvolts, we could detect changes of one or two microstrain. It all depended on having a very good voltmeter.
 

FAQ: Minimum microstrains that a wheatstone bridge or strain gauges will pick up?

What are minimum microstrains?

Minimum microstrains refer to the smallest amount of deformation that a material can experience before it is detected by a strain gauge. It is typically measured in microstrains (με), with 1 microstrain being equivalent to 0.0001% strain.

How does a Wheatstone bridge measure microstrains?

A Wheatstone bridge is a type of electrical circuit that uses four resistors to measure changes in electrical resistance. When a strain is applied to one of the resistors, its resistance changes, causing an imbalance in the bridge. This change in resistance can be measured and converted into a strain measurement, allowing for the detection of microstrains.

What types of materials can be measured for microstrains using a strain gauge?

A strain gauge can be used to measure microstrains in a wide range of materials, including metals, plastics, composites, and even biological tissues. However, the material must have some amount of electrical resistance and be able to withstand the application of a strain without breaking.

What factors can affect the sensitivity of a strain gauge or Wheatstone bridge?

The sensitivity of a strain gauge or Wheatstone bridge can be affected by several factors, including the gauge's size, shape, and material, the type and magnitude of the applied strain, and the environmental conditions such as temperature and humidity. It is essential to calibrate the gauge and consider these factors when making strain measurements.

What are the applications of measuring microstrains with a Wheatstone bridge or strain gauge?

Measuring microstrains with a Wheatstone bridge or strain gauge has a wide range of applications, including structural health monitoring, stress analysis in materials, load testing of bridges and buildings, and even in the development of medical devices and prosthetics. It allows for the precise measurement of small deformations, providing valuable data for various industries and research fields.

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