National Instruments SCXI-1345 User manual

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371177A-01 © Copyright 1993, 1994 National Instruments Corporation. All rights reserved.March 1993
NATIONAL
INSTRUMENTS®
The Software is the Instrument
®
Installation Guide
SCXI-1345 Shielded Cable
This guide describes how to install the SCXI-1345 shielded cable with an adapter board between
an SCXI module and a data acquisition board. In addition to the SCXI-1345 kit contents, you
will also need an SCXI chassis, an SCXI module, a computer, a multifunction I/O (MIO) board,
a small Phillips-head screwdriver, and a small flathead screwdriver.
Introduction
With the SCXI-1345 shielded cable, you can make a low-noise, long-distance connection
between your SCXI chassis and your MIO board. You can use the SCXI-1345 with the
following MIO boards:
PC/XT, PC AT Macintosh
AT-MIO-16 NB-MIO-16
AT-MIO-16F-5 NB-MIO-16X
AT-MIO-16X
The SCXI-1345 shielded cable consists of a 1, 2, 5, or 10 m round cable that has a 50-pin female
connector with a grounding strap at one end and a 68-pin female connector at the other end.
When plugged into the SCXI-1345 adapter board, the shielded cable brings the pinout of the
MIO board I/O connector to the SCXI module and to a breakout connector you can use with
other SCXI accessories, such as the SCXI-1180 and the SCXI-1351.
What Your Kit Should Contain
The SCXI-1345 shielded cable kit is available in four cable sizes: 1, 2, 5, or 10 m.
In addition, each version of the kit contains the following components:
¥ Cable adapter assembly
¥ Two small screws
¥ Replacement bracket for AT-MIO-16 boards

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¥ Replacement bracket for NB-MIO-16 boards
¥ Two cable tie wraps
¥SCXI-1345 Shielded Cable Installation Guide
If your kit is missing any of the components, contact National Instruments.
Installation Procedure
Figure 1 illustrates the components of your SCXI system and how to connect them.
SCXI Module
Adapter
Board
Step 3 Step 4
Step 7
Shielded Cable
Grounding Strap
Step 8
Step 9
MIO Data Acquisition Board
Figure 1. Connecting the SCXI-1345 to Your MIO Board and SCXI Module
Perform the following steps to install the SCXI-1345 cable:
1. Turn off the power to your computer and the SCXI chassis.
2. Install your SCXI module in the SCXI chassis, following the instructions in your module
user manual.
3. Plug the socket connector of the SCXI-1345 adapter board into the rear signal connector of
the SCXI module.
4. Secure the SCXI-1345 adapter board by screwing the two screws through the rear panel of
the adapter board and into the threaded strips in the rear of the SCXI chassis.

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5. Replace the bracket of your MIO board with the appropriate bracket from the SCXI-1345
cable kit, unless your MIO board has a bracket with a grounding strap tab.
a. Remove your MIO board from your computer.
b. Unscrew and remove the two screws that attach the bracket to the MIO board.
c. Remove the bracket from the board. See Figure 2 for NB board bracket removal or
Figure 3 for AT board bracket removal.
Step c
Step b
Step b
Bracket
NB MIO Board
Figure 2. Removing the Bracket from an NB Board

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Step c
Step b
Step b
AT MIO
Board
Bracket
Figure 3. Removing the Bracket from an AT Board
d. The 50-position I/O connector on your MIO board may have small plastic key inserts
installed for mating with military polarized connectors. Because these keys are not
compatible with the 50-position connector on the SCXI-1345, you must remove them.
The 50-position SCXI-1345 connector has a center polarization bump that prevents you
from inserting the connector upside down.
To remove the key inserts, use a thin probe such as a pencil or pen tip to gently press
down on the release tab in the center of the key insert (see Figure 4). Then use the
probe to lift up the back end of the key insert and slide the insert off the connector.

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MIO Board
Figure 4. Removing the Key Inserts
e. Identify the proper replacement bracket from your kit. If you have an NB Series board,
use the bracket marked 745402-01; if you have an AT Series board, use the bracket
marked 745403-01. The bracket that you use should look like the one you remove,
except that the new one has an extra tab that attaches to the grounding strap.
f. Install the new bracket by aligning the bracket with the holes in your MIO board and
screw in the two mounting screws.
6. Install your MIO board in a slot in your computer, following the instructions in your MIO
board user manual.
7. Connect the 68-pin connector (the end without the grounding strap) of the SCXI-1345
cable to the 68-pin connector of the SCXI-1345 adapter board as shown in Figure 5.
Adapter
Board
Shielded Cable
Figure 5. Cable to Adapter Board Connection

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8. Connect the 50-pin connector (the end with the grounding strap) of the cable to the I/O
connector on the MIO board as shown in Figure 6.
Shielded Cable
Grounding Strap
Step 8
Step 9
MIO Data Acquisition Board
Figure 6. Cable to I/O Connector Connection
9. Slide the end lug of the ground strap onto the tab of the MIO bracket.
10. Secure the cable to a fixed object with the tie wraps to relieve the strain on the cable.
Strain relief is needed because the SCXI-1345 shielded cable is considerably stiffer than
ribbon cable. The cable connector also has a long stiff backshell that can exert leverage on
the MIO board connector.
The finished installation should look like Figure 7.
Computer
SCXI-1345
Shielded Cable
SCXI
Chassis
Figure 7. Installed Cable

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Grounding Considerations
The SCXI-1345 cable has an outer shield, which is grounded to the SCXI chassis at one end
when you connect the SCXI-1345 cable to the chassis. The other end of the cable terminates in a
grounding strap that provides shielding for the MIO board when connected. You do not have to
connect the grounding strap for the system to function; however, connecting the grounding strap
improves the electrostatic discharge immunity of the SCXI system, reduces electromagnetic
interference, and shields the analog signals from noise. National Instruments recommends that
you connect the grounding strap. On the other hand, connecting the grounding strap may
increase the ground current flowing between the SCXI system and the computer, thus increasing
the noise in some applications. Laboratory tests with the grounding strap connected produced
less noise, but you can try it both ways and decide which way works better for your application.
If you leave the grounding strap unconnected, secure it to the cable with a tie wrap so that the
strap does not dangle and brush against the exposed pins of another connector at the back of your
computer.
SCXI-1345 Shielded Cable Assembly Pin Translations
The SCXI-1345 cable assembly ties pins 1 and 2 (AIGND) of the MIO board I/O connector
together and ties pins 24 and 33 (DGND) of the MIO board I/O connector together. Do not use
the SCXI-1345 cable assembly with any data acquisition board other than an MIO-16. All other
numbered pins only connect to the same pin number on all three connectors.