Measurement Crosstalk Errors

Crosstalk refers to changes in both sensitivity and output produced in all parallel circuits by a resistance change in any one of the circuits. As is the case with the calibration error, this occurs because the resistance changes in each of the parallel circuits affect the voltage applied to -- and consequently, the output from -- all the other circuits.

Output errors can be partially generalized to yield a "crosstalk sensitivity index" like that shown here. The approximate incremental output that will occur in each of the other circuits as the result of a 1000 microstrain change in any one circuit is given by this graph.

Range of nominal incremental output produced in companion parallel circuits by a strain change of 1000 microstrain in any one circuit when the initial resistance of all active and dummy gages is the same, common and individual leadwires are all of the same resistance, and the circuit has been shunt calibrated at 1000 microstrain across the active gages, assuming a package gage factor of 2.000.

Note that this incremental output is not directly related to the magnitude of any other output that may be present due to strain in the affected circuits. Rather, these incremental outputs can be thought of as "output shifts" that are algebraically added to each of the indicated strains in the affected circuits. When the extent of the incremental outputs caused by crosstalk must be known more precisely, Eq. ( 516.3 ) should be used to calculate the outputs of all circuits under any set of "instantaneous" resistances. The errors produced by crosstalk are relatively small in comparison to those that can arise from the loss of leadwire temperature compensation as described in the following section.

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