National Instruments 321906B-01 用户手册
Chapter 1
Routing Signals with Your NI 2501/2503
1-2
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National Instruments Corporation
Refer to Appendix B,
, for more information on terminal blocks
you can order from National Instruments.
You can also use multiple NI 2501/2503 cards together to expand the size
of the multiplexer or matrix. For example, you can connect two cards to
create a 48 x 1 two-wire multiplexer or a 12 x 4 two-wire matrix.
of the multiplexer or matrix. For example, you can connect two cards to
create a 48 x 1 two-wire multiplexer or a 12 x 4 two-wire matrix.
Caution
The maximum voltage is different for the NI 2501 and NI 2503 switch cards.
If you intend to use more than one type of card, be sure you do not exceed the
maximum voltage of any card in your system. Refer to Appendix A,
If you intend to use more than one type of card, be sure you do not exceed the
maximum voltage of any card in your system. Refer to Appendix A,
,
for information.
Analog Bus
The NI 2501/2503 works with a four-wire analog bus. You connect the
analog bus to the switch card through its main front-panel connector.
You can use the analog bus to simplify connecting multiple cards to an
instrument such as a digital multimeter (DMM). This bus makes it possible
to create large systems using multiple switch cards.
analog bus to the switch card through its main front-panel connector.
You can use the analog bus to simplify connecting multiple cards to an
instrument such as a digital multimeter (DMM). This bus makes it possible
to create large systems using multiple switch cards.
For example, if you have two NI 2501/2503 cards—or one of each—in two
adjacent slots, you can connect them through the analog bus and create a
48 x 1 two-wire multiplexer. With this flexibility, you keep the wiring of
the modules to a minimum while you create large switching solutions. In
such cases, the scanning architecture uses some of the PXI trigger lines for
synchronization and delivers full access to all of the scanning features for
the cards. The National Instruments software you receive with the
NI 2501/2503 handles the complexity of programming the cards.
adjacent slots, you can connect them through the analog bus and create a
48 x 1 two-wire multiplexer. With this flexibility, you keep the wiring of
the modules to a minimum while you create large switching solutions. In
such cases, the scanning architecture uses some of the PXI trigger lines for
synchronization and delivers full access to all of the scanning features for
the cards. The National Instruments software you receive with the
NI 2501/2503 handles the complexity of programming the cards.
Triggers
Two triggers are used to handshake the NI 2501/2503 switch with PXI
instruments or other external instruments. The
instruments or other external instruments. The
trigger
indicates when the card has closed all the necessary switches for the next
scan and the switches have settled, or
scan and the switches have settled, or
. This trigger is typically
wired to a measurement device, such as a DMM, which is configured to
take a reading when it receives the trigger.
take a reading when it receives the trigger.
The External Trigger Input trigger is sourced by another instrument, such
as the DMM, and causes the NI 2501/2503 to advance to the next entry
in the scan list. The triggers can be routed to the front connector of the
NI 2501/2503, to any of the PXI TTL triggers, or to the PXI star trigger. If
no external trigger input is available, you can have the software trigger the
NI 2501/2503 to advance to the next entry in the scan list.
as the DMM, and causes the NI 2501/2503 to advance to the next entry
in the scan list. The triggers can be routed to the front connector of the
NI 2501/2503, to any of the PXI TTL triggers, or to the PXI star trigger. If
no external trigger input is available, you can have the software trigger the
NI 2501/2503 to advance to the next entry in the scan list.
!