Strain Gauges. How do I pick the right one?

[Koopatryhard]

I'm trying to learn how to pick the right strain gauge for my application and looking around I see a lot of information and I can wade through that for the most part to get what I need but there are some questions that I can't find answers for. Maybe with a little more google-fu I could but I wanted an opinion from a real person.

First off I would like to mount to something lighter than aluminum; ideally I'd want to use a plastic. Looking at HBMs website it looks like there are a few options such as PVC, Polyimide, and Polyamide. I certainly could use aluminum if I have to but I'm trying to minimize weight as much as possible. I'm wondering though is this going to really be a pain in the neck to measure strains with? I understand the bonding procedure is a little harder but will the plastic make things that much harder? Also, will I need to look at other specialized strain gauges that work specifically with plastics? If so, what should I look for?

Secondly, I'm wondering about placement on the load cell. I have approximately 100 lbs being distributed over four axially loaded cells. I was thinking of doing a half bridge configuration on each to balance out simplicity and noise reduction. Is there a good spot on the load cell to place the gauges? After running a few analyses I've found what look to be the highest concentrations of strain in the material and I was thinking that would give me the best sensitivity for the gauge. Is this correct or should I look for something else?

Finally, what are going to be the most important things to look at for getting the right one? Anything that I should specifically hone in on so I don't make any rookie mistakes?

Thanks in advance for your help.
Cheers.

[jboggs]

Welcome to the forum. Unfortunately I can't really help you with your problem, at least not directly. I have an observation from several decades of experience the engineering world. Back in the day when all we had was paper catalogs and telephones, that's what we used. You ended up developing relationships with commonly used vendors and manufacturers. You learned to count on manufacturers to help you figure out the best way to use their products. They're called Application Engineers. Its their job to help you solve your problem. I have noticed an interesting phenomenon as the internet and Google and forums like this one become the default "go-to" for today's young engineers. It seems to never cross their minds to actually call a live person at a manufacturer and ask them for help. If they don't see the information they want on a website, they search somewhere else. Call somebody. You didn't mention that you did that, but maybe you did. If so I apologize for my little rant. I can tell you this - there is a world of intelligence and experience on this forum but there is probably NO one on this site that could help you as much as a few phone calls directly to strain gage manufacturers' application engineers. Not their sales desk (order takers), their application engineers. Try that and see what you learn.

[akashram]

There is a pdf for strain gauge selection:

Open Strain Gauge selection document: tn505.pdf