Help An issue with a cantilever tube instrumented with strain gauges.

AI Thread Summary
The discussion revolves around issues faced in developing a cantilever tube instrumented with strain gauges, particularly concerning unexpected output readings when applying small loads. The user questions the sensitivity of the gauges and considers factors like lead wire resistance and soldering quality. Additionally, there is a request for guidance on writing a C++ program to save data from two DAQ cards, highlighting the user's inexperience with programming. Suggestions include checking the zero load null and gauge factor, as well as seeking resources in a programming sub-forum. The conversation emphasizes the need for troubleshooting both hardware and software aspects of the project.
babistopher
Messages
15
Reaction score
0
I am working on the development of an instrument which can be simply thought of as a cantilever tube. This tube is instrumented with strain gauges to measure the X/Y strains and two sets of rosettes, each consisting of two strain gauges at 45 degree. Note that the X/Y are 3-wire half bridge and the rosettes (for torque) are full bridge. I have been having several issues with this instrument and I am trying to figure them out one at a time.

First of all, when I apply a small load (around 1 N) I get an output of around 12 N if not more. Would anyone know why the gauges seem to be so sensitive to the loads? I have taken into consideration the gains of the amplifier and filter in the circuit. Would lead wire resistance be the culprit despite it being a 3-wire connection (which apparently negates its effect)? What about soldering? That's my first of many questions! Any help is appreciated!
 
Engineering news on Phys.org
The first things I would look at are your zero load null and the gauge factor input into your readout system.
 
Sorry I didn't reply back. I had to work on something else for the past couple of weeks. Thanks for that. I'll look into those things whenever I can.

I do, however, have a more urgent task at hand and was hoping you could help me out. I am supposed to write a program using C++ that will take data collected by two separate DAQ cards and save them as either a text or spreadsheet file. Now, I'm still new at C++ and I do not even know where to begin. I have been looking for some literature or tutorials that might guide me online but I have had no luck. Would you know of any sites I could look into for that? Thanks.
 
Sorry. I am not a programmer. I haven't done anything outside of Labview when it comes to DAQ. I don't even think I could tell you what the first line of C++ code should say.
 
babistopher said:
I have been looking for some literature or tutorials that might guide me online but I have had no luck. Would you know of any sites I could look into for that? Thanks.

Try the Programming sub-forum...

https://www.physicsforums.com/showthread.php?t=15689
 

Thread 'Query on Isentropic relationships (such as PV^gamma = constant)'

Hi all, I have a question. So from the derivation of the Isentropic process relationship PV^gamma = constant, there is a step dW = PdV, which can only be said for quasi-equilibrium (or reversible) processes. As such I believe PV^gamma = constant (and the family of equations) should not be applicable to just adiabatic processes? Ie, it should be applicable only for adiabatic + reversible = isentropic processes? However, I've seen couple of online notes/books, and...
View full post »

Thread 'Dry sump pump issue'

I have an engine that uses a dry sump oiling system. The oil collection pan has three AN fittings to use for scavenging. Two of the fittings are approximately on the same level, the third is about 1/2 to 3/4 inch higher than the other two. The system ran for years with no problem using a three stage pump (one pressure and two scavenge stages). The two scavenge stages were connected at times to any two of the three AN fittings on the tank. Recently I tried an upgrade to a four stage pump...
View full post »

Similar threads

Deriving Strain in Cantilever Beam with Known Deflection
Replies
4
Views
6K
Designing an instrument with strain gauges
Replies
6
Views
5K
How Can Strain Gauges Be Used to Design an Effective Accelerometer?
Replies
1
Views
4K
Wheatstone bridge with four active strain gauges - extension cable length compensation formula
Replies
8
Views
2K
Can Strain Gauges Achieve 0.01 mN Sensitivity for 3D Force Sensing?
Replies
1
Views
3K
How do I determine the K value from a cantilever beam deflection test?
Replies
1
Views
5K
Pipeline bend calculation from strain gauge data
Replies
3
Views
2K
Tube/Bar Rigidity: Which Offers Most?
Replies
2
Views
4K
Measurement technology textbook problems
Replies
2
Views
413
How to Determine Maximum M and T in a Cantilever Shaft?
Replies
3
Views
5K

Hot Threads

Recent Insights

Back
Top