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Configuration and Installation
Chapter 2
AT-MIO-16D User Manual
2-50
© National Instruments Corporation
Cabling and Field Wiring
This section discusses cabling and field wiring guidelines for the AT-MIO-16D board.
Field Wiring Considerations
Accuracy of measurements made with the AT-MIO-16D can be seriously affected by
environmental noise if proper considerations are not taken into account when running signal wires
between signal sources and the AT-MIO-16D board. The following recommendations mainly
apply to analog input signal routing to the AT-MIO-16D board, though they are applicable for
signal routing in general.
You can minimize noise pickup and maximize measurement accuracy by doing the following:
•
Use individually shielded, twisted-pair wires to connect analog input signals to the
AT-MIO-16D. With this type of wire, the signals attached to the CH+ and CH- inputs are
twisted together and then covered with a shield. This shield is then connected 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.
•
Use differential analog input connections to reject common-mode noise.
The following recommendations apply for all signal connections to the AT-MIO-16D:
•
Physically separate AT-MIO-16D signal lines from high-current or high-voltage lines. These
lines are capable of inducing currents in or voltages on the AT-MIO-16D signal lines if they
run in parallel paths at a close distance. Reduce the magnetic coupling between lines by
separating them by a reasonable distance if they run in parallel, or by running the lines at right
angles to each other.
•
Do not run AT-MIO-16D signal lines through conduits that also contain power lines.
•
Protect AT-MIO-16D signal lines from magnetic fields caused by electric motors, welding
equipment, breakers, or transformers by running the AT-MIO-16D signal lines through
special metal conduits.
MIO-16 Cabling Considerations
National Instruments has a cable termination accessory–the CB-100–for use with the AT-MIO-
16D board. This kit includes two terminated 50-conductor flat ribbon cables and two 50-pin CB-
50 connector blocks. You can attach signal I/O leads to screw terminals on the connector block
and thereby be connected to the AT-MIO-16D I/O connector.
The CB-100 is useful for prototyping an application or in situations where AT-MIO-16D
interconnections are frequently changed. Once you develop a final field wiring scheme, however,
you may want to develop your own cable. This section contains information and guidelines for
design of such a cable.
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