Chapter 2 Connecting Signals
© National Instruments Corporation 2-7 SCXI-1125 User Manual
Temperature Sensor Connection
Pin C4 on the front signal connector is used to connect to a terminal block
temperature sensor. The temperature sensor channel is not isolated and is
referenced to the chassis ground. The connection is overvoltage protected
to ±25 VDC with power on and ±15 VDC with power off.
Rear Signal Connector
The rear signal connector is a 50-pin male ribbon cable connector used for
analog signal connectivity and communication between the
SCXI-1125 and the connected DAQ device. The rear signal connector
allows the DAQ device to access all eight differential analog output signals
from the SCXI-1125. The positive terminal of each analog output is
CH x + and the negative terminal CH x –. Grounding signals, AI GND
and OUT REF, provide reference signals needed in the various analog
referencing modes on the E/M Series DAQ device. In multiplexed mode,
the CH 0 signal pair is used for sending all eight channels of the
SCXI-1125, and other analog signals from other modules, to the connected
E/M Series DAQ device. If the module is directly connected to the E/M
Series DAQ device, the other analog channels of the E/M Series DAQ
device are still unavailable for general-purpose analog input because they
are still connected to the amplifier outputs of the SCXI-1125 in multiplexed
mode.
The communication signals between the DAQ device and the SCXI system
are SER DAT IN, SER DAT OUT, DAQ D*/A, SLOT 0 SEL*, SER CLK,
and AI HOLD COMP, AI HOLD. The digital ground, D GND on pins 24
and 33, provides a separate ground reference for the communication
signals. SER DAT IN, SER DAT OUT, DAQ D*/A, SLOT 0 SEL*, and
SER CLK are the communication lines for programming the SCXI-1125.
The AI HOLD COMP, AI HOLD and SYNC signals are the signals
necessary for multiplexed mode scanning. If the E/M Series DAQ device is
connected to the SCXI-1125, these digital lines are unavailable for
general-purpose digital I/O. The rear signal pin assignments are shown in
Table 2-2.