I recently graduated from Virginia Tech in May in ME. There was one project I was working on with a vibrations lab that, was and is, past my current abilities and comfort zone. I initially took it because that's what I wanted, a challenge, but I had problems limiting the scope of the project and subsequently, I ended up choking on all that I bit off. Honestly, it was very frustrating and left me not thinking very highly of myself. It's never fully left my mind, but it's been a little bit and I want to try to finish it!
The project is a low-cost modal testing apparatus for use in graduate classes. I went through a number of iterations, starting naively with an arduino uno as the data collection/ADC. Since I now have a little disposable income, I got a DAQ https://www.dataq.com/products/di-1100/ and a couple accelerometers that get me more than sufficient resolution in terms of acceleration. I am planning on doing post-processing in MATLAB. I am planning on doing impulse testing with roaming hammer/accelerometer. I'm shooting for being able to identify the first 5-10 modes shape of a reasonably compliant system.
Right now I'm looking for a reasonable load cell to use. The force sensing resistors, from my experience, seem like they would have too low repeatability... and accuracy honestly, they're more for detecting changes in pressure. The canister ones with screws are all in the $800 range, which makes sense as they are likely the lions-share of an impulse hammer, which start around $1500. The button ones that I have seen are all very high load. The one I got(I super glued a piece of pointy plastic to it so I had something to hit the beam with) had a very low output voltage, so I got an instrumentation amplifier (2 actually, but I'm pretty sure I fried one with my soldering iron and the other is stuck misaligned until the heat gun I ordered here). It's possible that the instrumentation amplifier I've been working on is still alive, but breaking out the SOIC was very confusing to me, it's possible I missed up the translation. Am I approaching this right? Is there a better solution for what I'm doing that one of you more experienced engineers could guide me towards? I can either either purchase more instrumentation amplifiers or get different ones or...
I'm looking for some guidance, either technical or overarching or maybe for another bonehead ME to commiserate with me. Anyway, thanks for coming to my TedTalk.
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