Chapter 3
Theory of Operation
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National Instruments Corporation
3-11
an input signal, which results in an increase in measurement resolution and
accuracy.
After isolation, further filtering is available to increase the noise immunity
of the amplifier channel. It is important to note that the overall amplifier
bandwidth is determined by both filtering stages, so to achieve the required
bandwidth, both filtering sections should be set the same, as indicated in
Chapter 2,
Configuration and Installation
.
Excitation Output Channels
In addition to the four input channels, the SCXI-1121 contains four fully
isolated excitation channels, each corresponding to an input channel. For
instance, input channel 0 corresponds to excitation channel 0. Each
excitation channel consists of a voltage/current source with overvoltage
protection and current limiting. Two levels of excitation are available for
each mode of operation. In the voltage mode you can set the level to
3.333 V or 10 V in the current mode you can set the level to 150 µA or
450 µA. You can choose one configuration out of the four available. To
configure the excitation channels refer to Chapter 2,
. The excitation channels are isolated from each other and are
independently configurable for voltage or current excitation.
Calibration
For information about calibrating the SCXI-1121, refer to the
SCXI-1121
Calibration Procedure
document.