Chapter 2
Using Your NI 4472
NI 4472 User Manual
2-12
ni.com
other ADEs, refer to
Synchronizing Multiple PCI-DSA Devices:
Select_Signal
in
NI-DAQ Function Reference Help
(
Start»Programs»
National Instruments»DAQ»NI-DAQ Help)
.
♦
NI 4472 for PXI/CompactPCI
To synchronize two or more NI 4472 devices in a PXI/CompactPCI system,
one must be located in PXI Slot 2. This device is the master, and the
NI 4472 devices in other slots are slaves. The master broadcasts the ADC
oversample clock to the other NI 4472 devices on the PXI Star trigger lines,
and uses the RTSI 5/TRIG 5 line to synchronize the start of the acquisition.
For specific LabVIEW programming instructions, refer to
Synchronizing
Multiple PXI-DSA Devices
in
LabVIEW Help
(
Start»Programs»National
Instruments»LabVIEW 6»LabVIEW Help
). For using NI-DAQ with
other ADEs, refer to
Synchronizing Multiple PXI-DSA Devices:
Select_Signal
in
NI-DAQ Function Reference Help
(
Start»Programs»
National Instruments»DAQ»NI-DAQ Help)
.
Device Configuration Issues
Selecting a sample rate that is less than two times the frequency of a band
of interest can lead you to believe the device is functioning improperly.
By undersampling the signal, you might receive what appears to be a
DC signal. This situation is due to the sharp antialiasing filters that
remove frequency components above the sampling frequency. If you have
a situation where this occurs, simply increase the sample rate until it meets
the requirements of the
Nyquist Sampling Theorem
. For more information
on the filters and aliasing, refer to the
section of
Chapter 3,
Device Overview and Theory of Operation
Note
Unlike other converter technologies, delta-sigma converters must be run
continuously and at a minimum clock rate to operate within specifications. Although the
software will let you use a lower sample rate, you must
always
use a sample rate of at least
1.0 kS/s to ensure the accuracy of your data acquisition.