Programming instructions

Chapter 21 Common SCXI Applications
LabVIEW Data Acquisition Basics Manual 21-16
© National Instruments Corporation
strain is applied (always measure at the beginning of the VI);
Bridge
Configuration
;
Vex
, the excitation voltage;
Rl
, the lead resistance; and
Rg
,
the resistance of the strain gauge before strain is applied. You can usually
ignore the lead resistance,
Rl
, for strain gauges unless the leads are several
feet. For more information on any of the parameters for this VI, refer to
Chapter 30,
Signal Conditioning VIs
, in the
LabVIEW Function and VI
Reference Manual
, or refer to the LabVIEW
Online Reference
, by selecting
Help»Online Reference…
.
Analog Output Application Example
You can output isolated analog signals using the SCXI-1124 analog output
module. If you use the DAQ Channel Wizard to configure your analog
output channels, generating signals using the SCXI-1124 is no different
from the techniques in Part III,
Making Waves with Analog Output
.
The remainder of this section describes how to generate signals with the
SCXI-1124 when you do not use the DAQ Channel Wizard.
The SCXI-1124 can generate voltage and current signals. Refer to the
example analog output VI, SCXI-1124 Update Channels VI, located in
labview\examples\daq\scxi\scxi_ao.llb
. This VI uses the analog
output Advanced VIs because the output mode (whether you have voltage
or current data) must be accessible in order to change the value, as shown
in Figure 21-10. The program calls the AO Group Config VI to specify
the device and output channels. The AO Hardware Config VI specifies
the output mode and the output range, or limit settings, for all the channels
specified in the channels string. This advanced-level VI is the only place
where you can specify a voltage or current output mode. If you are
going to output voltages only, you may want to use the AO Config VI
(an Intermediate VI), instead of the AO Group Config and AO Hardware
Config VIs. You can program individual output channels of the SCXI-1124
for different output ranges by using the arrays for channels, output mode,
and limit settings. The AO Single Update VI initiates the update of the
SCXI-1124 output channels. To help debug your VIs, it is always helpful to
display any errors, in this case using the Simple Error Handler VI.