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Chapter 3
Signal Connections
3-18
ni.com
Caution
Do not connect the +5 V power pin directly to D GND, RG, or any pin config
u
red
for o
u
tp
u
t on the NI 660
x
device, or any voltage so
u
rce or o
u
tp
u
t pin on another device.
Doing so can damage the device and the comp
u
ter. National Instr
u
ments is not liable for
damages res
u
lting from s
u
ch a connection.
I/O Signals
Field Wiring Considerations
To prevent incorrect res
u
lts ca
u
sed by environmental noise and crosstalk,
make s
u
re the NI 660
x
and the peripheral device share a common gro
u
nd
reference. Connect one or more NI 660
x
device D GND lines to the gro
u
nd
reference of yo
u
r peripheral device.
Yo
u
can also
u
se the digital filters available on each PFI line to red
u
ce
errors that these problems might ca
u
se.
Noise
For noise imm
u
nity, take the following preca
u
tions:
•
When ro
u
ting signals to the TIO device, keep cabling away from noise
so
u
rces.
•
Separate the TIO device signal lines from high-c
u
rrent or high-voltage
lines. High-c
u
rrent or high-voltage lines that r
u
n in parallel paths at a
close distance can ind
u
ce c
u
rrents in or voltages on the TIO device
signal lines. To red
u
ce the co
u
pling between lines, separate parallel
lines by a reasonable distance or r
u
n the lines at right angles to one
another.
•
Do not r
u
n signal lines thro
u
gh cond
u
its that also contain power lines.
•
Protect signal lines from magnetic and electric fields ca
u
sed by
monitors, electric motors, welding eq
u
ipment, breakers, transformers,
or other devices by r
u
nning them thro
u
gh special metal cond
u
its.
•
Use appropriate digital filtering to remove noise.