Question

Answer the following

a)State any advantages or disadvantages you see in measuring vibrations with a strain gauge as opposed to the other methods we have used. What effect would changes in temperature have on strain gauge readings and is it possible to eliminate this effect? It was briefly mentioned that different bridge configurations can eliminate temperature effects, but what are those effects and how does that work?

b)In order to get the most accurate readings, should a strain gauge have a high stiffness or a low stiffness? Explain.

Answer 1

Explanation:- Strain gauge is a device which is generally used to measure the strain of an object. Basically we can say it is a sensor which changes their resistance with applied load, it converts force, pressure and tension in to a change of resistance which can be measured.

Advantages - There are many advantages of strain gauge over other vibration measurement methods as follows-

• There is no moving part in strain guge.
• size of strain gauge is small.
• It is inexpansible device.
• it has better frequency response.
• Hystersis characteristics are good over other method.
• High value of gauge Factor.

Disadvantages: - There are many disadvantages of strain gauge over other method as follows-

• It has poor linearity.
• Strain gauge are very sensitive to temperature changes.
• It needs to be caliberated.
• sensitive to distortion signals.

effect of change of temperature- the lead wire resistance Vary with temperatures and it affect the accuracy of strain gauge measurement. The change of lead wire resistance produce error in static measurement. it is occur when the lead wire resistance is so small. this is considering the coefficeint of temperatue of copper is greater than coefficeint of temperatue of gauge. This can be minimised by using bridging configuration.

Elimination of Temperature Effect - The temperature effect would be eliminate by using Half bridge and full bridge sensor.By using two or four strain gauges in wheat- stone bridge we can minimize the temperature effect, this is known as Half bridge and Full bridge configuration. because the temperature changes are identical to reaistance ratio of gaugea which does not change along this output voltage of the gauge does not change. this is the simplest method to minimize the temperature effect which is called "Half-bridge and Full-bridge configuration" .

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b) Explanation:- For Better accurate reading the strain gauge should have low stiffness. Because low stiffness leads to greater elongation capability, greater resistance to premature failure and gives a high performance range.