Bridge Balance - HBM Genesis GEN5i User Manual

GEN5i

Bridge balance

The bridge circuit is only in balance (has no output when the bridge voltage is
applied) provided that R1 / R2 = R4 / R3. Taking into account the various
resistance tolerances on the strain gage(s), resistors and leadwires, an initial
unbalance is invariably present. Adjustment of initial balance so that at zero
strain there is zero output is achieved by bridge balancing.
While resistive-balance circuits are widely used in strain gage instrumentation,
the GN410 and GN411 uses an alternative electronic method of balancing the
output to zero involving measuring the output of the bridge and injecting an
equal and opposite voltage. This method permits rapid automatic balancing in
multi-channel systems and eliminates the bridge loading errors that are
possible in the resistive system when making measurements with precision
strain gage transducers.
HINT/TIP
When doing a bridge balance, the GN410 and GN411 acquisition card
measures the input value at the connector of the acquisition card. This means
it cannot "see" if a bridge is actually connected or not. When no voltage is
present this can be since the bridge is balanced or that no bridge is connected.
Bridge balancing in Perception is done through the Bridge Balance dialog.
Figure 12.22: Bridge Balance dialog
A Balance command
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