How can I measure accuracy of strain gage placement

Hello,

I need some advice on how to inspect strain gage placement inside a load cell. Typically strain gages have alignment marks, the gage itself is small at (0.25" x 0.14" ). The gage is bonded in the center of a hole (0.55" dia) drilled through inside the load cell (which is basically a

5"x1" block of steel).

Currently gage placement is visually alligned to scribed lines. During the bonding process it is possible for the gage to slip translationally as well as rotationally.

I need a way to measure how far off the allignment from the scribe lines are. I was wondering if there is some lighted, flexible, boroscope with a reticule????

I really have no ideas, any comments or suggestions would be greatly appreciated.

Thank you for your time Qu1nn

Reply to
qu1nn
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Dear qu1nn:

Couldn't you simply challenge the assembly with a known load, and calibrate?

David A. Smith

Reply to
N:dlzc D:aol T:com (dlzc)

David, Yes it is common practice to modify the wheatstone bridge to compensate for flaws in the bonding/material that will occur.

My goal is specific to a quality function. Again, I need to measure position inside a hole and I need a good tool.

Thanks qu1nn

Reply to
qu1nn

Dear qu1nn:

Forgive my probing.

It seems like the response-per-pound would *tell* you relatively where the strain gauge was in the arrangement. Since response is a function of displacement, displacement a function of location (and load).

No further response required to me, since I don't think I helped...

David A. Smith

Reply to
N:dlzc D:aol T:com (dlzc)

David,

Dont worry, that is cool. Actually there are way, way too many variables to make that direct correlation. material properties, material preparation, gage handling, gage tolerances, bonding pressure, glueline consistency, soldering, thermal effects...the list goes on and on.

Thanks again Qu1nn

Reply to
qu1nn

There are lots of borescopes to be had; how much do you want to spend is the big question.

I'd question the need for a reticle though; you'd probably be better off with video and a simple machine vision application.

Reply to
Michael

I seem to remember a small "periscope" used by army sergeants to inspect how clean a rifle barrel was......

Reply to
Jonathan Barnes

If you have the reference marks and geometry as known wouldn't a boroscope that captures a digital image be used with post processing the image?

---------- Ed Ruf Lifetime AMA# 344007 ( snipped-for-privacy@EdwardG.Ruf.com)

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Reply to
Ed Ruf

First question is it half or full bridge combination of strain gages?

If you have these combinations, you can compesate errors of placements of strain gages and temperature influences when calibrate your load cell. Better control if you are working with one straing gage, that you put another on opposite side, but first must explain where you wish to put them to i can give you better answer?

Songman_hr!

486 still rides
Reply to
pjesnik

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