Section 7. Installation
297
7.7.12.6.1 FieldCalStrain() Shunt Calibration Concepts
1. Shunt calibration does not calibrate the strain gage itself.
2. Shunt calibration does compensate for long leads and non-linearity in the
resistive bridge. Long leads reduce sensitivity because of voltage drop.
FieldCalStrain()
uses the known value of the shunt resistor to adjust the gain
(multiplier / span) to compensate. The gain adjustment (S) is incorporated by
FieldCalStrain()
with the manufacturer's gage factor (GF), becoming the
adjusted gage factor (GF
adj
), which is then used as the gage factor in
StrainCalc()
. GF is stored in the CAL file and continues to be used in
subsequent calibrations. Non-linearity of the bridge is compensated for by
selecting a shunt resistor with a value that best simulates a measurement near
the range of measurements to be made. Strain-gage manufacturers typically
specify and supply a range of resistors available for shunt calibration.
3. Shunt calibration verifies the function of the CR6.
4. The zero function of
FieldCalStrain()
allows a particular strain to be set as an
arbitrary zero, if desired. Zeroing is normally done after the shunt calibration.
Zero and shunt options can be combined ina single CRBasic program.
CRBasic example
FieldCalStrain() Calibration
(p. 298)
is provided to demonstrate
use of
FieldCalStrain()
features. If a strain gage configured as shown in figure
Quarter-Bridge Strain Gage with RC Resistor Shunt
(p. 298)
is not available, strain
signals can be simulated by building the simple circuit, substituting a 1000 Ω
potentiometer for the strain gage. To reset calibration tests, use the support
software
File Control
(p. 583)
menu to delete .cal files, and then send the
demonstration program again to the CR6.
Example Case: A 1000 Ω strain gage is placed into a resistive bridge at position
R1. The resulting circuit is a quarter-bridge strain gage with alternate
shunt-resistor (Rc) positions shown. Gage specifications indicate that the gage
factor is 2.0 and that with a 249 kΩ shunt, measurement should be about 2000
microstrain.
Send CRBasic example
FieldCalStrain() Calibration
(p. 298)
as a program to a CR6
datalogger.
7.7.12.6.2 FieldCalStrain() Shunt Calibration Example
CRBasic example
FieldCalStrain() Calibration
(p. 298)
is provided to demonstrate
use of
FieldCalStrain()
features. If a strain gage configured as shown in figure
Quarter-Bridge Strain Gage with RC Resistor Shunt
(p. 298)
is not available, strain
signals can be simulated by building the simple circuit, substituting a 1000 Ω
potentiometer for the strain gage. To reset calibration tests, use the support
software
File Control
(p. 583)
menu to delete .cal files, and then send the
demonstration program again to the CR6.
Case
: A 1000 Ω strain gage is placed into a resistive bridge at position R1. The
resulting circuit is a quarter-bridge strain gage with alternate shunt-resistor (Rc)
Содержание CR6 Series
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Страница 76: ...Section 5 Overview 76 FIGURE 20 Half Bridge Wiring Example Wind Vane Potentiometer ...
Страница 80: ...Section 5 Overview 80 FIGURE 23 Pulse Input Wiring Example Anemometer ...
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Страница 251: ...Section 7 Installation 251 FIGURE 46 Running Average Frequency Response FIGURE 47 Running Average Signal Attenuation ...
Страница 454: ...Section 8 Operation 454 FIGURE 104 Narrow Sweep High Noise ...
Страница 459: ...Section 8 Operation 459 FIGURE 106 Vibrating Wire Sensor Calibration Report ...
Страница 535: ...Section 8 Operation 535 8 11 2 Data Display FIGURE 121 CR1000KD Displaying Data ...
Страница 537: ...Section 8 Operation 537 FIGURE 123 CR1000KD Real Time Custom ...
Страница 538: ...Section 8 Operation 538 8 11 2 3 Final Storage Data FIGURE 124 CR1000KD Final Storage Data ...
Страница 539: ...Section 8 Operation 539 8 11 3 Run Stop Program FIGURE 125 CR1000KD Run Stop Program ...
Страница 541: ...Section 8 Operation 541 FIGURE 127 CR1000KD File Edit ...
Страница 542: ...Section 8 Operation 542 8 11 5 PCCard Memory Card Management FIGURE 128 CR1000KD PCCard Memory Card Management ...
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Страница 549: ...Section 9 Maintenance Details 549 FIGURE 133 Separate Back Shell from Module FIGURE 134 Disconnect Battery Connector ...
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Страница 610: ...Section 11 Glossary 610 FIGURE 137 Relationships of Accuracy Precision and Resolution ...
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