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National Instruments NI 784xR, NI 785xR Single-Ended Connections for Grounded Signal Sources (NRSE Input Mode)

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Chapter 2 Hardware Overview ofthe NI 78x xR

© National Instruments Corporation 2-15 R Series Intelligent DAQ User Manual

Single-Ended Connections for Grounded Signal Sources (NRSE Input Mode)

To measure a grounded signal source with a single-ended input mode, you

must configure the NI 783xR/784xR/785xR in the NRSE input mode. Then

connect the signal to the positive input of the NI 783xR/784xR/785xR

instrumentation amplifier and connect the signal local ground reference to

the negative input of the instrumentation amplifier. The ground point of the

signal should be connected to AISENSE. Any potential difference between

the NI 783xR/784xR/785xR ground and the signal ground appears as a

common-mode signal at both the positive and negative inputs of the

instrumentation amplifier. The instrumentation amplifier rejects this

difference. If the input circuitry of a NI 783xR/784xR/785xR is referenced

to ground in RSE input mode, this difference in ground potentials appears

as an error in the measured voltage.

Figure 2-9 shows how to connect a grounded signal source to a channel on

the NI 783xR/784xR/785xR configured for NRSE input mode.

Figure 2-9. Single-Ended Input Connections for Ground-Referenced Signals

–

+

–

+

–

+

–

+

Vcm

Vs

I/O Connector

AISENSE

AIGND

Vm

AI+

AI– Instrumentation

Amplifier

Measured

Voltage

Ground-

Referenced

Signal

Source

Common-

Mode

Noise and

Ground

Potential

NRSE Input Mode Selected

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