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Appendix B
Troubleshooting
B-2
ni.com
reference. There are vario
u
s methods of achieving this reference while
maintaining a high common-mode rejection ratio (CMRR). These methods
are o
u
tlined in the
Connecting Analog Input Signals on
and
Connecting Analog Input Signals on
sections of Chapter 4,
.
AI GND is an AI common signal that ro
u
tes directly to the gro
u
nd
connection point on the devices. Yo
u
can
u
se this signal if yo
u
need a
general analog gro
u
nd connection point to the device. Refer to the
Use Differential Connections with Ground-Referenced Signal Sources
section of Chapter 4,
, for more information.
How can I use the AI Sample Clock and AI Convert Clock signals on a
USB-621
x
device to sample the AI channel(s)?
USB-621
x
devices
u
se AI Sample Clock and AI Convert Clock to perform
interval sampling. As Fig
u
re B-1 shows, AI Sample Clock controls the
sample period, which is determined by the following eq
u
ation:
1/sample period = sample rate
Figure B-1.
AI Sample Clock and AI Convert Clock
AI Convert Clock controls the convert period, which is determined by the
following eq
u
ation:
1/convert period = convert rate
This method allows m
u
ltiple channels to be sampled relatively q
u
ickly in
relationship to the overall sample rate, providing a nearly sim
u
ltaneo
u
s
effect with a fixed delay between channels.
Ch
a
nnel 0
Ch
a
nnel 1
Convert Period
Sa
mple Period