NI SCXI-1127, Руководство пользователя

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Chapter 2 U s i n g the SCXI-1127
Outo— 411
Out0+ 41
Out2 .4I
Out2+
OA+
OA-
16-to-1
Multiplexer
15A+
15A-
•
EXCITATION Multiplexer
OB+
OB-
16-to-1
Multiplexer
155+
156-
•
l •
l •
ABO+
ABO—
ABO
Switch
SENSE Multiplexer
4-:
•---•
AB2+
AB2—
AB2
Switch
Figure 2-6. Four-Wire Block Diagram
HVAB
Backplane
When used with an NI-DMM for four-wire ohms measurement, the upper
differential multiplexer provides the excitation source for the four-wire
channel being scanned.
The EXCITATION input to the upper multiplexer is available through the
OUTO+ and OUTO- screw terminals on the SCXI-1331. The SENSE output
from the lower 16-to-1 multiplexer is available through the OUT2+ and
OUT2- screw terminals on the SCXI-1331. You can also connect the
EXCITATION and SENSE commons of the SCXI-1127 to the HVAB
backplane. Use switches ABO and AB2 to make this connection. You can
do this through NI-SWITCH. This is the recommended usage with the
NI-DMM.
Figure 2-7 shows an example of a four-wire channel configuration of the
SCX1-1331 terminal block. Channel 6 consists of channel 6A+ and 6A-,
and 6B+ and 6B-. Channel 6A of four-wire channel 6 is the excitation
channel and channel 6B is the voltage sense channel. Therefore, to make a
four-wire resistance measurement for example, a DMM should excite the
current through high-voltage ABO or OUTO using channel 6A and sense the
voltage across the resistor through AB2 or OUT2 using channel 6B.
© National Instruments Corporation 2-7 S C X 1 - 1 127 User Manual