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Contents
SCXI-1141/1142/1143 User Manual vi ni.com
Chapter 4
Theory of Operation
Power-Up State.............................................................................................................. 4-1
Digital Control Circuitry ............................................................................................... 4-3
Input Amplifiers ............................................................................................................4-3
Correcting Gain and Offset Errors..................................................................4-4
Lowpass Filters..............................................................................................................4-5
Filter Theory ................................................................................................... 4-5
Performance of the SCXI-1141/1142/1143 Module Filters............................ 4-6
Magnitude Response.........................................................................4-6
Phase Response.................................................................................4-8
Setting the Cutoff Frequency............................................................4-11
Using the SCXI-1141/1142/1143 Module as an Antialiasing Filter............... 4-12
Using the External Clock Input....................................................................... 4-14
DC-Correction Circuitry and Overload Recovery .......................................... 4-15
Filter Bypass Mode.........................................................................................4-16
Rear Connector Analog Outputs ...................................................................................4-16
Multiplexed Mode (Recommended)............................................................... 4-16
Parallel Mode.................................................................................................. 4-17
Chapter 5
Using the SCXI-1141/1142/1143 Module
Developing Your Application in NI-DAQmx...............................................................5-1
Typical Program Flowchart ............................................................................5-1
General Discussion of Typical Flowchart.......................................................5-3
Creating a Task Using DAQ Assistant or Programmatically........... 5-3
Adjusting Timing and Triggering.....................................................5-3
Configuring Channel Properties....................................................... 5-4
Acquiring, Analyzing, and Presenting..............................................5-7
Completing the Application..............................................................5-7
Developing an Application Using LabVIEW.................................................5-7
Using a NI-DAQmx Channel Property Node in LabVIEW.............5-9
Specifying Channel Strings in NI-DAQmx ....................................................5-10
Text Based ADEs .............................................................................5-10
Programmable NI-DAQmx Properties ............................................. 5-12
Calibration.....................................................................................................................5-13
External Calibration........................................................................................ 5-13
Appendix A
Specifications