Can you just use a dial gauge.... measures to 1/1000" usually

Dik

> A high-end theodolite can detect angular changes <10 arcsec, so at any distance under 5 m, 0.01-in changes can be detected

> There are lots of laser distance measurement systems with micron-level range resolutions. An extension of those are the 3D scanners: https://www.creaform3d.com/en/metrology-solutions/...

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Thanks to both of you for the suggestions!!

Well a rude method would be a plumb bob suspended from the beam by a very long string; then measure before and after loading. Give time for the string to stretch when measuring before loading.

How long is the lever arm to produce the 0.010 inch movement under load?
What is your "anchor" point, and how will you verify IT has not moved under the load that deflected the beam?

Example: Your deflected is horizontal, 20 feet long. You attach the "anchor" to the vertical column nearby, then apply the load to the horizontal beam. The load deforms the vertical beam as well, and your "measurement" is "zero" - Because the vertical beam twisted the measurement lever arm down just as far as the beam deflected down under the load.

I just bought a laser rangefinder on eBay: http://www.ebay.com/sch/i.html?_sop=15&_from=R... Most of these are repeatable to around 1 mm, which is 0.004 inch. They use a visible, red, laser, and so long as your placement and target are repeatable, you could detect 0.01 inch changes.

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My Hilti laser rangefinder has an accuracy of 3mm for ranges up to 200m. I originally purchased it to measure heights of cable trays from the floor.

Dik

IR - Check that please, 1 mm ~ 0.040 inch.

sorry, too early in the morning...

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Mt laser hilti also as a continuous range function. Set it up under your beam, turn it on and leave it in place. Load up your beam and the meter measures and records the +/- change.