( ... continued )

Basic Wheatstone bridge circuit.

Considering, for the moment, resistance changes in and (composing the right-hand branch of the bridge circuit), the output voltage after such changes is:

      (514.11)

The change in the output signal from the bridge (or the nulling voltage) is then:

  (514.12)

In the usual case, however, , the nominal strain gage resistance. After making this substitution, and reducing,

 (514.13)

For the quarter-bridge circuit with only a single active gage( ), = 0 and :

             (514.14)

Or, introducing the relationship from Eq. ( 514.4 ),

              (514.15)

( continued ... )

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