Campbell CR800 Series - Strain Measurements - Details

Section 8. Operation
343
Calibrate() Instruction Results
Cal()
Array
Field
Descriptions of Array Elements
Typical Value
Differential (Diff)
Single-Ended (SE)
Offset or Gain
±mV Input
Range
Integration
52 SE Offset 2.5 50 Hz Rejection ±20 LSB
53 Diff Offset 2.5 50 Hz Rejection ±20 LSB
54 Gain 2.5 50 Hz Rejection –0.00067 mV/LSB
8.1.2.5 Strain Measurements — Details
Related Topics:
• Strain Measurements — Overview (p. 70)
• Strain Measurements — Details
(p. 343)
• FieldCalStrain() Examples
(p. 228)
A principal use of the four-wire full bridge is the measurement of strain gages in
structural stress analysis. StrainCalc() calculates microstrain (µε) from the
formula for the particular strain bridge configuration used. All strain gages
supported by StrainCalc() use the full-bridge schematic. In strain-gage parlance,
'quarter-bridge', 'half-bridge' and 'full-bridge' refer to the number of active
elements in the full-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 table StrainCalc()
Instruction Equations
(p. 343) 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.
StrainCalc() Instruction Equations
StrainCalc()
BrConfig Code Configuration
1
Quarter-bridge strain gage
1
:
2
Half-bridge strain gage
1
. One gage parallel to strain, the
other at 90° to strain: