National Instruments PXIe-4339, User Manual And Specifications, Page: 22 / 36

22 | ni.com | NI PXIe-4339 and RM-4339 User Guide and Terminal Block Specifications
Quarter-Bridge Completion and Shunt Calibration
The RM-4339 provides software selectable quarter-bridge completion resistors that enable the
NI PXIe-4339 to be used with quarter-bridge strain gages. You can select 120
Ω , 350 Ω or 1 k Ω
completion resistors.
Quarter-bridge shunt calibration resistors are also provided on the RM-4339. These resistors are
labeled SCB_50k and SCB_100k in the switch circuit diagram of Figure 8. There are two
different shunt calibration resistance values that you can select; 50 k
Ω and 100 k Ω . The
quarter-bridge shunt calibration resistors are dedicated to the quarter-bridge completion resistors
and are selectable through NI-DAQmx. NI recommends using the 50 k
Ω shunt calibration
resistor for shunt calibration of 120 Ω quarter-bridge strain gages and using the 100 k Ω shunt
calibration resistor for 350 Ω and 1 k Ω quarter-bridge strain gages.
If quarter-bridge completion is not used, the QTR/RS- pin of the RJ50 connector is connected to
the RS- pin of the NI PXIe-4339. Refer to the
NI PXIe-4339 User Manual
for more information
about quarter-bridge measurements.
You can access SCB_50k and SCB_100k using NI-DAQmx attributes/properties.
LabVIEW property names and locations:
•
AI.Bridge.ShuntCal.ShuntCalBResistance
• Location:
AI»General Properties»Signal Conditioning»Bridge»ShuntCal»Shunt Cal
B Resistor Value
• AI.Bridge.ShuntCal.ShuntCalBActualResistance
• Location:
AI»General Properties»Signal Conditioning»Bridge»Shunt Cal B Actual
Resistor Value
Shunt Resistors
The RM-4339 provides built-in 100 k Ω shunt resistors that can be programmatically connected
to the SCA terminal pairs on the RJ50 connectors. In addition you can use the optional
SCAL-4339 Shunt Calibration Accessory to provide user provided shunt calibration resistors to
the SCA terminals of each channel. Refer to the
External Shunt
section for more information.
Refer to Table 7 for signal names and descriptions.
You can choose between built-in 100 k Ω resistors and external user provided resistors using an
NI-DAQmx channel attribute/property.
LabVIEW property names and locations:
•
AI.Bridge.ShuntCal.ShuntCalASrc
• Location:
AI»General Properties»Signal Conditioning»Bridge»ShuntCal»Shunt Cal
A Source
• Possible values: BuiltIn or UserProvided