SCXI Cascading: SCXI-1120 to SCXI-114x

Cascading SCXI modules gives users greater flexibility in conditioning analog signals. It allows you to combine the functionality of multiple SCXI modules to perform one data acquisition process. This example program demonstrates the use of two SCXI modules in a cascaded system. The first stage is an SCXI-1120, which provides high voltage isolation and signal amplification. The output signals from the SCXI-1120 are passed to the SCXI-114x, which filters the incoming signals using an 8th order programmable lowpass filter. The exact frequency response of the filter depends on which SCXI module you are using. The SCXI-1141 is an Elliptical filter, the SCXI-1142 is a Bessel filter, and the SCXI-1143 is a Butterworth filter. Please see the SCXI-114x user manual for more details on the frequency, step, and phase response of each module.

Because cascading programatically adjustable SCXI modules such as the SCXI-1141/2/3 is an advanced application for only advanced users, National Instruments strongly recommends using a combination of hardware and digital (or software) filtering to achieve equivalent results as cascading an isolation module with a hardware filter (such as the SCXI-1120) with filtering module. An anti-aliasing filter is necessary and can be provided by the SCXI-112x. Digital filtering can provide equivalent results for noise & error reduction with greater flexibility than hardware filters. Review ch4 of the LabVIEW Analysis Concepts manual in related links below for more information.

While cascading SCXI modules provides additional opportunities for creating complete signal conditioning solutions, users should excercise greater care when configuring and calibrating a cascaded SCXI system. Improper programming of cascaded modules can actually lead to decreased accuracy in your measurements. Cascading SCXI modules is thus recommended only for more advanced users.

Instructions for use are attached below.

Related Links:

LabVIEW Analysis Concepts

Getting Started with SCXI

Requirements

Filename: exampleinstructions.txt

Software Requirements

Application Software: LabVIEW Professional Development System 7.0
Language(s): C#, Basic, C

Hardware Requirements

Hardware Group: Multifunction DAQ (MIO)
Driver: NI-DAQmx 7.0

Filename: 1120_114x.llb

Software Requirements

Application Software: LabVIEW Full Development System 6.0
Language(s): Basic, C, C#

Hardware Requirements

Hardware Group: Multifunction DAQ (MIO)
Driver: Traditional NI-DAQ (Legacy) 6.9.1

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