Chapter 3
Configuring and Testing
©
National Instruments Corporation
3-7
NI PXI-4220 User Manual
Note
For most NI PXI-4220 applications, you should set the autozero mode to
None
.
Autozero is not useful for relative transducers such as strain gauges. Autozero performs a
software compensation for offset voltage from the signal conditioning and DAQ circuitry,
not the transducer, and is therefore not as accurate as hardware offset null compensation.
10. Ensure that you have selected the strain channel(s) you wish to
calibrate in the
Channel List
box, and then click
Calibration
to
perform offset null compensation and shunt calibration on the strain
channel(s).
11. On the screen that opens, you can choose to enable offset null
compensation and/or shunt calibration, and enter the shunt calibration
resistor information. Click
Next
.
12. The
Measure and Calibrate
screen displays information specific to
the strain channel(s). Click
Measure
to acquire a signal from the strain
channel(s) and
Reset Data
to reset the values to default. Click
Calibrate
to calibrate the strain channel(s). When you have completed
calibrating the strain channel(s), click
Finish
.
Note
For offset null compensation and shunt calibration of quarter-bridge configuration
types, the value of the quarter-bridge completion resistor must equal the nominal resistance
of the strain gauge.
13. If you are creating a task and want to set timing or triggering controls,
enter the values in the
Task Timing
and
Task Triggering
tabs.
Creating a Custom Voltage with Excitation Global
Channel or Task
Use the
Custom Voltage with Excitation NI-DAQmx Task
or
Global
Channel
when measuring load, force, torque, pressure, or other
bridge-based sensors. To create an
NI-DAQmx
Custom Voltage with
Excitation Task
or
NI-DAQmx Global Channel
, complete the following
steps:
1.
Double-click the
Measurement & Automation Explorer
icon on the
desktop.
2.
Right-click
Data Neighborhood
and select
Create New
.
3.
Select
NI-DAQmx Global Channel
or
NI-DAQmx Task
and
click
Next
.
4.
Select
Analog Input
, and then select
Custom Voltage with
Excitation
.
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