To simulate a compressive surface strain, , by shunting in the preceding figure the calibration resistor is calculated from:

  (514.24)

And, for a simulated tensile strain, , generated by shunting ,

  (514.25)

When substituting into Eqs. (514.24) and (514.25), the signs of the simulated strains must always be carried, of course. Also, it is apparent that leadwire resistance, if present, affects the nonlinear behavior, and must be known to permit exact simulation. Since the expressions are relatively insensitive to the quantity , precision measurement of the leadwire resistance is not ordinarily required. After scaling the instrument at a simulated strain, , the registered strain is precisely correct for only that same magnitude. When necessary, the corrected strain at any level can be calculated from:

  (514.26)

The notation in Eq. (514.26) is the same as in Eq. ( 514.18 ) for the quarter-bridge circuit.

( continued ... )

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