Contents
Daily Dose 010 | INSTRUMENTATION & DATA ACQUISITION
How do you measure strain with a strain gage?
Measure strain with a strain gage – a problem type found within the subject of Instrumentation and Data Acquisition , one of those “gray area” subjects.
It’s not all out Electrical theory or Material Science, but is out there enough to scare many of us – but it can easily become a subject you are looking forward to working on the exam once you are exposed to some of the basic theories within.
In this video, we jump in to a problem that is covered within the subject of INSTRUMENTATION & DATA ACQUISITION, specifically walking you through how to measure strain using a strain gage.
This is a collegiate themed scenario for all of you Gator fans, so enjoy.
Key Definition
What is a STRAIN GAGE?
A STRAIN GAGE, which you may also see spelled as STRAIN GAUGE, is a sensor whose resistance varies with applied force.
A STRAIN GAGE converts force, pressure, tension, weight, etc., into a change in electrical resistance which can then be measured.
When external forces are applied to a stationary object, stress and strain are the result.
Stress is defined as the object’s internal resisting forces, and strain is defined as the displacement and deformation that occur.
The Process
How can you measure strain with a strain gage?
Many are intimidated by much of what is found within the subject of Instrumentation and Data Acquisition – especially when it comes to using measurement devices.
One such device is the strain gage.
Using a strain gage is like giving a voice to silent materials. They tell us their stories of stress and stretch, which we, as engineers or scientists, interpret to design safer bridges, more resilient materials, and innovative products.
And for that reason, understanding and tackling these problem types with confidence is important.
Let’s walk through a streamlined, step-by-step approach to measure strain with a strain gage:
- Step 1: Understand the Problem
- Step 2: Determine the Change in Resistance
- ΔR = Rnew − Roriginal
- Step 3: Calculate the Strain Using the Gage Factor
- ε = ΔR / (Roriginal × GF)
- Step 4: Calculate the Deformation (Change in Length)
- ΔL = ε × Loriginal
- Step 5: Interpret the Results
- Step 6: Additional Considerations (if needed)
- Step 7: Document and Review
Carefully read through the problem statement and identify any given values (original resistance, change in resistance, gage factor, original length, etc.) and pinpoint what you are being asked to solve for (change in length, strain, etc.)
Use the following general formula to determine the change in resistance:
To determine strain from the change in resistance, employ the gage factor and the general formula:
Compute the resultant force using the Pythagorean theorem:
Ensure that your result is sensible. If the deformation seems excessively large or small, review your calculations.
Consider physical implications: For instance, if calculating strain for a building material, very high values might indicate a risk of failure.
Sometimes, problems can be more complex and may involve temperature changes, multiple loading conditions, or use of multiple strain gauges. Always ensure you consider any additional data or steps provided in the problem.
Make sure to clearly document each step. This not only makes checking your work easier but is also good practice for real-world engineering tasks.
Review the problem one last time to ensure you didn’t miss any details.
This is the general blueprint that will help you tackle a range of problems involving strain gauges. Adapt and expand upon these steps as needed based on specific nuances found within the problem statement.
And with all of that being stated, check out the video and see how we can go about solving this type of problem in the most efficient manner.
As always, we are here to help, Prepineer
