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Chapter 2
Configuration and Installation
©
National Instruments Corporation
2-21
The input signal range of an SCXI-1121 input channel is ±5 V/G
total
referenced to its negative input, where G
total
is equal to the product of the
first-stage and second-stage gains. In addition, the input channels are
overvoltage protected to 250 V
rms
with power on or off at a maximum of
4.5 m
Arms
sink or source.
Caution
Exceeding the input signal range and the common-mode input range results in
distorted signals. Exceeding the maximum input voltage rating (250 V
rms
between positive
and negative terminals and between any terminal and earth ground) can damage the
SCXI-1121, the SCXIbus, and the DAQ board. National Instruments is
not
liable for any
damages or injuries resulting from such signal connections.
Excitation Channels
Four fully isolated excitation channels are available. Each excitation
channel corresponds to an input channel. A 250 V
rms
isolation barrier exists
between two corresponding channels (for example, between input
channel 0 and excitation channel 0). In addition, the excitation outputs are
overvoltage protected to 250 V
rms
with current foldback.
Caution
Exceeding the overvoltage protection or isolation rating on the excitation output
can damage the SCXI-1121, the SCXIbus, and the DAQ board. National Instruments is
not
liable for any damages or injuries resulting from such signal connections.
Temperature Sensor Connection
Pins C2 and C4 are dedicated for connecting the temperature sensor to the
SCXI-1121. The temperature sensor is not isolated and is referenced to
chassis ground. The connection is overvoltage-protected to ±25 VDC with
power on and ±15 VDC with power off.
Caution
Exceeding the overvoltage protection on the temperature connections can damage
the SCXI-1121, the SCXIbus, and the DAQ board. National Instruments is
not
liable for
any damages resulting from such signal connections.