NI SCXI-1127, Руководство пользователя

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Chapter 2 U s i n g the SCXI-1127
One-Wire Channel Scanning Configuration
The SCXI-1127 has 64 one-wire channels in the multiplexer mode that are
available through the SCXI-1331 terminal block. Figure 2-4 shows the
SCXI-1127 configured as a 64-to-1 one-wire multiplexer. One-wire
configuration provides a high channel count because all input signals have
the same reference. This common reference, called 1_WIRE_LO_REF on
the SCXI-1127, is available to you through the screw terminals on the
SCXI-1331 terminal block.
Out0+ .11
OutO—
1 — WIRE — LO —REF
ci—
i —
64-to-1
Single-ended
Multiplexer
ABO
Switch
Figure 2-4. One-Wire Block Diagram
HVAB
Backplane
The output of the 64-to-1 multiplexer is available through the OUTO+ and
OUTO- screw terminals on the SCXI-1331. You can also connect the output
of the SCXI-1127 to the HVAB backplane using switch ABO to make the
connection.
On power up, switch ABO is open, disconnecting the SCXI-1 127 from the
high-voltage bus. If you are using the module with a high-voltage
backplane, you need to close the ABO switch to connect the multiplexer
output to the HVAB backplane. You can do this through NI-SWITCH.
Figure 2-5 shows an example of a one-wire configuration using the
SCXI-1331 terminal block. The diagram shows the one-wire terminal
block connections for channels 4, 24, and 59. Channel 4 (R1) is measuring
a resistance. The positive channel is labeled 4 while the negative terminal
(common reference) is labeled 1_WIRE_LO_REF.
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