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There are precision levels, one brand is the Taylor Hobson Talyvel. It has a small sensor unit that is about 5" square, and can easily detect arc second changes. Slipping a human hair under one end drives it completely off scale.

I have one obtained surplus on eBay. it reads out to 0.1 arc second and after factory calibration is supposed to be accurate to 0.2 arc second. When I put it on the bed of my 3500 Lb. lathe it easily detects the change when I walk from one end of the lathe to the other. The advantage of this is it has magnetic damping so that if you pick up the sensor and place it on a surface, it settles within 2 seconds! A water level or oil bubble master precision level takes at least 30 seconds to settle.

Jon