National Instruments SCXI-1121 User Manual - Introduction

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 National Instruments Corporation

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SCXI-1121 User Manual

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Introduction

This chapter describes the SCXI-1121; lists the contents of your 

SCXI-1121 kit; describes the optional software, optional equipment, and 

custom cables; and explains how to unpack the SCXI-1121 kit.

The SCXI-1121 consists of four isolated input channels and four isolated 

excitation channels. The SCXI-1121 is a module for signal conditioning of 

strain gauges, RTDs, thermistors, thermocouples, volt and millivolt 

sources, 4 to 20 mA current sources, and 0 to 20 mA process-current 

sources. The SCXI-1121 can operate in two output modes—the 

Parallel-Output mode with all four input channels connected in parallel to 

four data acquisition board channels, or the Multiplexed-Output mode with 

all four channels multiplexed into a single data acquisition board channel.

The SCXI-1121 operates with full functionality with National Instruments 

MIO-16 boards. The SCXI-1121 operates with full functionality with the 

Lab-PC+ board in single-chassis SCXI systems. However, the Lab-PC+ 

cannot control multiple-chassis SCXI systems. You can use the Lab-NB, 

the Lab-PC, the Lab-LC, and the PC-LPM-16 boards with the SCXI-1121, 

but these boards can control only single-chassis SCXI systems and cannot 

scan the module when it is configured in the Multiplexed-Output mode. 

These boards can perform only single-channel reads in this mode. You can 

also use the SCXI-1121 with other systems that comply with the 

specifications given in Chapter 2, 

Configuration and Installation

. You can 

multiplex several SCXI-1121s into a single channel, thus greatly increasing 

the number of analog input signals that can be digitized.

The addition of a shielded terminal block provides screw terminals for easy 

signal attachment to the SCXI-1121. In addition, a temperature sensor for 

cold-junction compensation of thermocouples is included on the terminal 

block. This cold-junction reference (CJR) is either multiplexed along with 

the four input channels or connected by jumpers to a different channel of 

the data acquisition board.

With the SCXI-1121, the SCXI chassis can serve as a fast-scanning signal 

conditioner for laboratory testing, production testing, and industrial 

process monitoring.