Chapter 4 Theory of Operation
SCXI-1125 User Manual 4-2 ni.com
Refer to the Configurable Settings in MAX section of Chapter 3,
Configuring and Testing, for more information about programmatically
setting gain using range settings in MAX. For more information about
programmatically setting gain using range settings in NI-DAQmx and
Traditional NI-DAQ (Legacy), refer to the Developing Your Application in
NI-DAQmx section or the Developing Your Application in Traditional
NI-DAQ (Legacy) section, respectively, of Chapter 5, Using the
SCXI-1125.
Filter Bandwidth and Cutoff Frequency
The SCXI-1125 provides two filtering stages with an overall response of a
four-pole Butterworth filter. You can control the cutoff frequency of the
filter through software. You can choose 4 Hz or 10 kHz. For additional
flexibility in cutoff frequency settings and for greater suppression, NI
recommends combining the hardware filtering provided by the SCXI-1125
with digital filtering. NI recommends using the Advanced Analysis
functions of LabVIEW, LabWindows/CVI, or Measurement Studio. By
combining hardware anti-aliasing with digital filtering, you can choose any
cutoff frequency.
The Advanced Analysis functions are only available in LabVIEW Full or
Professional Development Systems, and LabWindows/CVI Base or Full
Development Systems.
Refer to the Configurable Settings in MAX section of Chapter 3,
Configuring and Testing, for more information about programmatically
setting the cutoff frequency of the filter in MAX. For more information
about programmatically setting the cutoff frequency of the filter in
NI-DAQmx and Traditional NI-DAQ (Legacy), refer to the Developing
Your Application in NI-DAQmx section or the Developing Your
Application in Traditional NI-DAQ (Legacy) section, respectively, of
Chapter 5, Using the SCXI-1125.
Operating in Multiplexed Mode
You can configure the SCXI-1125 to operate in multiplexed mode as
described in Chapter 1, About the SCXI-1125. Using this mode of
operation, you can scan all input channels of the SCXI-1125 into one
output channel that is read by the National Instruments DAQ device. You
can also multiplex the CJC channel that connects to a sensor on the SCXI
terminal block for making temperature measurements.