Resistive-Bridge Type and
Circuit Diagram
CRBasic Instruction and
Fundamental Relationship
Relational Formulas
Three Wire
CRBasic Instruction:
Resistance3W()
Fundamental Relationship
2
:
1
Where X = result of the CRBasic bridge measurement instruction with a multiplier of 1 and an offset of 0.
2
Where Ri is the precision internal resistor value that is saved as part of the factory calibration procedure and Rs is
the sense resistance.
6.3.3 Strain measurements
A principal use of the four-wire full bridge is the measurement of strain gages in structural stress
analysis. StrainCalc() calculates microstrain (µɛ) from the formula for the specific bridge
configuration used. All strain gages supported by StrainCalc() use the full-bridge
schematic. 'Quarter-bridge', 'half-bridge' and 'full-bridge' refer to the number of active elements
in the bridge schematic. In other words, a quarter-bridge strain gage has one active element, a
half-bridge has two, and a full-bridge has four.
StrainCalc() requires a bridge-configuration code. The following table shows the equation
used by each configuration code. Each code can be preceded by a dash (-). Use a code without
the dash when the bridge is configured so the output decreases with increasing strain. Use a
dashed code when the bridge is configured so the output increases with increasing strain. A
dashed code sets the polarity of V
r
to negative.
6. Measurements 74
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