Two piles, 1 and 2, of carbon plates are clamped in yoke 6 by
means of screws 4. Lever 3, between piles 1 and 2, turns about
fixed axis A. This lever is attached to one of the strain gauge
points. The other point is carried by yoke 6. The instrument is
mounted on the structure being tested so that elongation is
transmitted to lever 3 by the point members. At this, lever 3
loads one pile and relieves the other. This reduces the resistance
of the first pile and increases th at of the second. Thus, the strain
of the item being tested is measured by determ ining the change
in resistance of the piles.
$4352$SmE,M$