Chapter 2 Configuration and Installation
© National Instruments Corporation 2-39 SCXI-1121 User Manual
The signals on the rear signal connector can be classified as analog output
signals, digital I/O signals, or timing I/O signals. Signal connection
guidelines for each of these groups are given in the following section.
Analog Output Signal Connections
Pins 1 through 12 and pin 19 of the rear signal connector are analog output
signal pins. Pins 1 and 2 are AOGND signal pins. AOGND is an analog
output common signal that is routed through jumper W33 to the analog
reference on the SCXI-1121. You can use these pins for a general analog
power ground tie point to the SCXI-1121 if necessary. In particular, when
using differential input data acquisition boards such as the MIO-16 series,
it is preferable to leave jumper W33 in its factory setting or in position
AB-R1 to avoid ground loops. With data acquisition boards that are
configured for referenced single-ended (RSE) measurements, W33 should
be in position AB-R0 to connect the SCXI-1121 ground to the data
acquisition analog ground. Pin 19 is the OUTREF pin this pin is connected
internally to the analog reference when jumper W33 is in position AB-R2.
Pins 3 through 12 are the analog output channels of the SCXI-1121. Pins 3
and 4 or MCH0± are a multiplexed output of all four input channels and the
temperature sensor output. Pins 5 through 10 or MCH1± through MCH3±
are a parallel connection of input channels 1 through 3 to the rear signal
connector. Pins 11 and 12 or MCH4± are a direct connection of the
temperature sensor. Notice that the temperature sensor is located on the
terminal block. For further details on configuring the temperature sensor
output, refer to the SCXI-1320, SCXI-1328, and SCXI-1321
TerminalBlocks section earli er in th is chapter.
Warning The SCXI-1121 analog outputs are not overvoltage-protected. Applying external
voltages to these outputs can damage the SCXI-1121. National Instruments is not liable for
any damages resulting from such signal connections.
Note The SCXI-1121 analog outputs are short-circuit protected.