1) Measuring instrument
Found on
https://www.crosswordclues.com/clue/strainmeter
A strainmeter is an instrument used by geophysicists to measure the deformation of the Earth. Linear strainmeters measure the changes in the distance between two points, using either a solid piece of material (over a short distance) or a laser interferometer (over a long distance, up to several hundred meters). The type using a solid length standa...
Found on
http://en.wikipedia.org/wiki/Strainmeter
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