Chapter 4
Signal Connections
©
National Instruments Corporation
4-29
PCI-4451/4452/4453/4454 User Manual
•
Protect signal lines from magnetic fields caused by electric motors,
welding equipment, breakers, or transformers by running them through
special metal conduits.
♦
PCI-4451/4452
The following recommendations apply to all analog signal connections to
or from your PCI-4451/4452:
•
Use differential analog input connections to reject common-mode
noise.
•
Use individually shielded, twisted-pair wires to connect analog input
signals to the device. With this type of wire, the signals attached to the
+ACHx and
−
ACHx inputs are twisted together and then covered with
a shield. You then connect this shield only at one point to the signal
source ground. This kind of connection is required for signals traveling
through areas with large magnetic fields or high electromagnetic
interference.
The following recommendations apply for all digital signal connections
from your PCI-4451/4452:
•
The digital output signal integrity is greatly influenced by the length of
the cable being driven. Minimize cable lengths and use schmitt-trigger
devices to deglitch signals. Further conditioning may be required to
create a clean signal.
•
Always try to couple a ground with a signal to minimize noise pickup
and radiation.