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© National Instruments Corporation E-1 SCXI-1127/1128 User Manual
E
Common Questions
This appendix addresses common questions you may have while using
your SCXI-1127/1128 module.
How fast can I scan with the SCXI-1127/1128 module?
The fastest scan rate for the SCXI-1127 is 100 scans/s, and the fastest scan
rate for the SCXI-1128 is 1000 scans/s. Typically, when using a DMM to
make accurate measurements, the DMM requires hundreds of milliseconds.
Consequently, the DMM becomes the limiting factor in determining the
scan rate.
What should I do if the software detects the module, but the switches
do not switch?
• Verify that the switches do not switch. Close your application program
and then launch the soft front panel as described in the Set up and Test
document you received with your kit. The soft front panel shows the
state of each relay switch on the module. Try closing and opening the
switches using the low level switch functions.
• Check the return codes of the NI-SWITCH operation to ensure that
there are no errors (negative values) or warnings (positive values). You
can also use the NI-Spy utility, which is installed with NI-SWITCH,
to check for error codes.
• Finally, verify that your code is correct. For reference, see the
examples described in the NI-SWITCH Software User Manual.
NI-SWITCH also ships with several examples in source code.
Compare your algorithm to the ones in the examples.
What should I do if scanning does not work in the handshaking mode
with a third-party DMM?
• Ensure that you have configured the SCXI-1127/1128 and the
instrument to correctly route all the trigger lines. The output trigger
of the instrument should connect to the trigger input of the
SCXI-1127/1128. In addition, make sure the scanner advanced trigger
of the SCXI-1127/1128 connects to the input trigger of the instrument.