Shielding And Driven Guard - HBM Genesis GEN5i User Manual

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Figure 12.10: Shunt calibration completion plug-in module
A
User Quarter-Bridge Completion
B
User Half-Bridge Completion
C User Shunt Cal
D
JUMPER! Remove when installing Half
12.6.5

Shielding and driven guard

When long cable runs are required, the excitation leads and signal leads are
generally separately twisted and shielded within the cable to minimize the
cross-coupling that would otherwise occur.
The high-performance signal conditioners offers the "driven guard" system
where the input shield is connected only to the drive pin of the conditioner and
where the shield is driven to a potential equal to the common-mode voltage of
the bridge. The driven shield or guard therefore minimizes the potential
difference between the internal conductors and the shield, thereby reducing the
mutual capacitance between them and the electrostatic coupling between the
shield and the internal conductors. In all cases, the driven shield is terminated
only at the driven guard conditioner terminal where the driven shield is
surrounded by an outer shield that is terminated to ground preferably at the
strain gage installation site as shown in Figure 12.11.
- Bridge completion
GEN5i
I2679-4.0 en