SCXI - USB Data Acquisition and Switching System

Publish Date: Aug 08, 2013 | 19 Ratings | 3.53 out of 5 |  PDF

Table of Contents

  1. Overview
  2. USB Connectivity
  3. I/O Modules
  4. Terminal Blocks
  5. Chassis
  6. IEEE 1451.4 – Smart Sensor Support
  7. Measurement Services Software

1. Overview

National Instruments SCXI is a high-performance signal conditioning and switching platform for measurement and automation systems. Whether you need to measure sensors or raw signals, generate voltages or currents, monitor digital lines, or route signals with switching, SCXI provides a single, integrated data acquisition platform with USB connectivity for all of your signal conditioning and switching needs. An SCXI system consists of multichannel signal conditioning modules installed in one or more rugged chassis. You can choose from a wide selection of analog input, analog output, digital I/O, and switching modules to fit your application needs exactly. NI-DAQmx measurement services software controls every aspect of your SCXI system from configuration, to programming in LabVIEW, to low-level OS and device control.

Back to Top

2. USB Connectivity

The SCXI data acquisition and switching system features USB connectivity, which means the SCXI system can be automatically detected and configured by the host PC once a connection has been established. All signals are measured using a digitizer module such as the NI SCXI-1600. Once the data has been digitized, it is streamed over USB for analysis and presentation. This type of data acquisition and switching system can easily be interfaced with a laptop computer, creating a very rugged and portable solution. Additionally, SCXI can also be used to provide simplified USB connectivity for measurements in a laboratory environment.


See Also:
USB Data Acquisition and Control Module for SCXI

Back to Top

3. I/O Modules

SCXI modules condition analog and digital signals and sensors inputs. SCXI modules offer a variety of functionality including analog input, analog output, digital I/O, and switching to meet many different application requirements. Analog input modules amplify, isolate, filter, and multiplex input signals from thermocouples, strain gages, RTDs, thermistors, millivolt sources, voltage sources up to 250 Vrms, and current sources. Analog output modules provide isolated voltage and current outputs. Digital input and output modules provide isolation for digital signals up to 240 VDC. SCXI switch modules, which include multiplexers and matrices provide high-density and high-power signal routing – from DC to RF. You can build an independent switching system as a front-end for your instruments, taking advantage of seamless software integration with the most popular development environments. You can mix and match modules to any combination of analog input, analog output, digital I/O, and switching to meet application requirements.

See Also:
Analog Input Modules
Analog Output Modules
Switching Modules - Multiplexer/Matrix/General Purpose

Back to Top

4. Terminal Blocks

Terminal blocks are used to connect signals to SCXI modules. The most common SCXI terminal blocks contain screw terminals (and a strain relief) that provide secure connections to sensors and signals. Certain terminal blocks are designed to work with specific modules and provide signal conditioning for certain sensor types. For example, a terminal block used for measuring thermocouple voltages will contain cold-junction compensation circuitry. Terminal blocks used for connecting to strain gages will provide socketed resistors for bridge-completion and shunt calibration. Terminal blocks connected to high-voltage signals will contain attenuation circuity. Some SCXI terminal blocks even contain microcontrollers that communicate with IEEE 1451.4 (TEDS) smart sensors. IEEE 1451.4 terminal blocks, such as the SCXI-1314T shown below, provide direct sensor connectivity via RJ50 input connectors. With this design, sensors can easily and quickly be disconnected, connected, and auto-detected by the SCXI system.

 


See Also:
Front-Mounting Terminal Blocks
Rack-Mountable Terminal Blocks
DIN-Rail Mountable Terminal Blocks

Back to Top

5. Chassis


National Instruments SCXI modules are housed in a rugged, low-noise SCXI chassis, which power and control SCXI modules and conditioned signals. The unique SCXI chassis architecture includes the SCXIbus, which routes analog and digital signals and acts as the communication conduit between modules. Chassis control circuitry manages this bus, synchronizing the timing between each module. With this architecture, you can measure multiplexed input channels from several modules in several chassis.

See Also:
4-Slot Chassis
12-Slot Chassis
DC-Powered Chassis (4-Slot)

Back to Top

6. IEEE 1451.4 – Smart Sensor Support

The SCXI data acquisition system offers connectivity and communication with transducers manufactured with IEEE 1451.4 smart sensor technology. The IEEE 1451.4 standard, Mixed-Mode Interface for Smart Transducers, defines a mechanism for adding self-identification technology to traditional analog-mode sensors and actuators. Developed jointly by sensor manufacturers, instrumentation and software suppliers, and users, IEEE 1451.4 defines the concept of a mixed-mode transducer that supplies both an analog and digital interface. The analog electrical interface provides a signal reflecting the physical phenomenon (such as temperature, pressure, and force) in the traditional manner. An IEEE 1451.4 smart sensor, however, also provides a digital interface for communicating with an embedded memory device within the transducer. This memory contains the binary transducer electronic datasheet (TEDS) information that identifies and describes the sensor or actuator. The TEDS contains information such as sensor manufacturer, model number, serial number, measurement range, sensitivity, and calibration information. With IEEE 1451.4 smart sensor compatibility and USB connectivity, SCXI systems are virtually plug-and-play.

See Also:
NI Sensors Plug&Play

Back to Top

7. Measurement Services Software

National Instruments includes the robust NI-DAQmx measurement services software with all SCXI devices. NI-DAQmx controls every aspect of the SCXI system, from configuration to programming in LabVIEW to low-level OS and device control. Real-world data can be acquired quickly with measurement-ready virtual channels and the new DAQ Assistant. Applications can be built with measurement-specific VIs, functions, datatypes, and analysis integrations. Measurements can be taken faster and more reliably with optimized DMA data transfer and single-point I/O. NI-DAQmx works with LabVIEW, LabWindows/CVI, Visual Basic, C/C++, and C# in Windows 2000/NT/XP.


The National Instruments Measurement Hardware DDK is a driver development kit with development tools and a register-level programming interface for NI data acquisition hardware. This package is designed for OEM customers developing applications in OSs such as Linux and Mac OS X.

NI offers configuration-based data logging software, VI Logger , for interactive measurement configuration and data storage.
See Also:
NI Data Acquisition Software


Back to Top

Bookmark & Share

Ratings

Rate this document

Answered Your Question?
Yes No

Submit