When lever 1, tu rning about fixed axis A , is deflected to the
right, contacts 2 are closed, energizing w in d in g 3. The current
in w ind in g 3 heats b im e ta llic strip 4 so th at its free end a is
deflected because the strip is bent due to the unequal thermal
expansion of the metals m aking up the b im e ta llic strip. When
lever 1 is deflected to the left, contacts 2 are opened, de-energizing
w ind in g 3. At this, b im e ta llic strip 4 cools and its end a is
deflected to the right. The m otion of strip 4 is repeated at a distance
by identical strip 5, which is heated by a w ind in g connected
in series to w ind in g 3. End b of strip 5 is connected by
a lin k and tu rn in g pairs to hand с which turns about fixed axis B.
On a scale, hand с indicates the deflection of ends a and b of
bim e ta llic strips 4 and 5. This deflection is proportional to the
deflection of lever 1, which is linked to the strain gauge.
$4356$,SmE,M$