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National Instruments NI 784xR, NI 785xR Differential Connections for Ground-Referenced Signal Sources

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Chapter 2 Hardware Overview ofthe NI 78x xR

© National Instruments Corporation 2-11 R Series Intelligent DAQ User Manual

Differential Connections for Ground-Referenced Signal Sources

Figure2-6 shows how to connect a ground-referenced signal source to a

channel on the NI783xR/ 784xR/785xR configured in DIFF input mode.

Figure 2-6. Differential Input Connections for Ground-Referenced Signals

With this connection type, the instrumentation amplifier rejects both the

common-mode noise in the signal and the ground potential difference

between the signal source and the NI 783xR/784xR/785xR ground, shown

as Vcm in Figure 2-6. In addition, the instrumentation amplifier can reject

common-mode noise pickup in the leads connecting the signal sources to

the device. The instrumentation amplifier can reject common-mode signals

when V+in and V–in (input signals) are both within their specified input

ranges. Refer to the NI R Series Intelligent DAQ Specifications, available at

ni.com/manuals, for more information about input ranges.

DIFF Input Mode Selected

–

+

–

+

–

+

–

+

V

cm

V

s

I/O Connector

AISENSE

AIGND

V

m

AI+

AI–

Ground-

Referenced

Signal

Source

Common-

Mode

Noise and

Ground

Potential

Measured

Voltage

Instrumentation

Amplifier

Contents

Main Page Important Information Warranty Copyright Trademarks Patents Compliance Compliance with FCC/Canada Radio Frequency Interference Regulations Determining FCC Class FCC/DOC Warnings Class A Contents About This Manual Chapter 1 Introduction Chapter 2 Hardware Overview of the NI 78xxR Page About This Manual Conventions Related Documentation Reconfigurable I/O Documentation Page Additional Resources Introduction About the Reconfigurable I/O Device Using PXI with CompactPCI Overview of Reconfigurable I/O Reconfigurable I/O Concept Flexible Functionality User-Defined I/O Resources Device-Embedded Logic and Processing Reconfigurable I/O Architecture Reconfigurable I/O Applications Software Development LabVIEW FPGA Module LabVIEW Real-Time Module Cables and Accessories Custom Cabling Safety Information Page Page Hardware Overview of the NI 78xxR Figure 2-1. NI781xR Block Diagram Figure 2-2. NI7830R Block Diagram Chapter 2 Hardware Overview ofthe NI 78x xR National Instruments Corporation 2-3 R Series Intelligent DAQ User Manual Figure 2-3. NI7831R/7833R/784xR/785xR Block Diagram PCI/PXI/CompactPCI Bus NI 7811R Overview The NI 7811R has 160 bidirectional DIO lines and a Virtex-II XC2V1000 FPGA. NI 7813R Overview The NI 7813R has 160 bidirectional DIO lines and a Virtex-II XC2V3000 FPGA. NI 7830R Overview NI 7831R/7833R Overview NI 784xR Overview NI 785xR Overview Analog Input (Multifunction R Series Only) Input Modes Input Range Connecting Analog Input Signals Page Types of Signal Sources Floating Signal Sources Ground-Referenced Signal Sources Input Modes Figure 2-5 summarizes the recommended input mode for both types of signal sources. Figure 2-5. Summary of Analog Input Connections Differential Connection Considerations (DIFF Input Mode) Differential Connections for Ground-Referenced Signal Sources Differential Connections for Nonreferenced or Floating Signal Sources Single-Ended Connection Considerations Single-Ended Connections for Floating Signal Sources (RSE Input Mode) Single-Ended Connections for Grounded Signal Sources (NRSE Input Mode) Common-Mode Signal Rejection Considerations Analog Output Connecting Analog Output Signals Digital I/O Connecting Digital I/O Signals Page Page Page RTSI Trigger Bus PXI Local Bus (NI PXI-781xR/783xR Only) Page Chapter 2 Hardware Overview ofthe NI 78x xR National Instruments Corporation 2-23 R Series Intelligent DAQ User Manual Figure 2-12. PXI Star Trigger Connections in a PXI Chassis Switch Settings (NI 781xR/783xR Only) Note SW2 and SW3 are not connected. PXI Star* * A Slot 2 device ties the PXI Star Line to the PXI 10 MHz clock Slot 3 Page Page Page Page +5 V Power Source Device Fuse Replacement (NI 784xR/785xR Only) Page Field Wiring Considerations (NI 783xR/784xR/785xROnly) Calibration (NI 783xR/784xR/785xROnly) Loading Calibration Constants Internal Calibration External Calibration Page A Connecting I/O Signals Appendix A Connecting I/O Signals Figure A-1. NI 781xR Connector Pin Assignments and Locations R Series Intelligent DAQ User Manual A-2 ni.com Appendix A Connecting I/O Signals Figure A-2. NI 783xR/784xR/785xR Connector Pin Assignments and Locations National Instruments Corporation A-3 R Series Intelligent DAQ User Manual Table A-1. I/O Connector Signal Descriptions Caution Connections that exceed any of the maximum ratings of input or output signals Table A-2. NI78xx R I/O Signal Summary Connecting to 5B and SSR Analog Signal Conditioning (NI 783xR/784xR/785xR Only) Figure A-3 shows the connector pinouts when using the NSC68-262650 cable. Figure A-3. Connector Pinouts when Using NSC68-262650 Cable Connecting to SSR Digital Signal Conditioning AI 07 Connector DIO 015 Connector AO 07 Connector Figure A-4. Connector Pinouts when Using the NSC68-5050 Cable DIO 023 Connector DIO 2439 Connector B Using the SCB-68 Shielded Connector Block C Technical Support and Professional Services Page Glossary Numbers/Symbols A B C D Page I L M N O P R S T V W