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National Instruments NI 783xR Common-Mode Signal Rejection Considerations

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Chapter 2 Hardware Overview ofthe NI 783xR

© National Instruments Corporation 2-13 NI 783xR User Manual

positive and negative inputs of the instrumentation amplifier. The

instrumentation amplifier rejects this difference. If the input circuitry of a

NI7 83xR is referenced to ground in RSE input mode, this difference in

ground potentials appears as an error in the measured voltage.

Figure 2-8 shows how to connect a grounded signal source to a channel on

the NI 783xR configured for NRSE input mode.

Figure 2-8. Single-Ended Input Connections for Ground-Referenced Signals

Common-Mode Signal Rejection Considerations

Figure 2-5 and Figure 2-8 show connections for signal sources that are

already referenced to some ground point with respect to the NI 783xR.

In these cases, the instrumentation amplifier can reject any voltage caused

by ground potential differences between the signal source and the device.

With differential input connections, 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 Appendix A, Specifications, for more

information about input ranges.

NRSE Input Mode Selected

–

+

–

+

–

+

–

+

Vcm

Vs

Ground-

Referenced

Signal

Source

Common-

Mode

Noise and

Ground

Potential

I/O Connector

AISENSE

AIGND

VmMeasured

Voltage

Instrumentation

Amplifier

AI+

AI–

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 783xR Page About This Manual Conventions Reconfigurable I/O Documentation Related Documentation Introduction About the NI 783xR 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 Optional Equipment Custom Cabling Safety Information Page National Instruments Corporation 2-1 NI 783xR User Manual Hardware Overview of the NI 783xR RTSI/PXI Triggers Connector 0 (MIO) PCI/PXI/CompactPCI Bus Figure 2-1. NI7830R Block Diagram NI 7830R Overview NI 7831R/7833R Overview Analog Input User- Configurable FPGA on RIO Devices Connector 0 (MIO) Input Modes Input Range Connecting Analog Input Signals Page Types of Signal Sources Floating Signal Sources Ground-Referenced Signal Sources Input Modes Figure 2-4. 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 Page 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 RTSI Trigger Bus PXI Local Bus (for NI PXI-783xR only) Switch Settings Page Page Power Connections Field Wiring Considerations Calibration Loading Calibration Constants Internal Calibration External Calibration A Specifications Analog Input Input Characteristics Accuracy Information DC Transfer Characteristics Dynamic Characteristics Settling Time Analog Output Output Characteristics Accuracy Information DC Transfer Characteristics Voltage Output Dynamic Characteristics Digital I/O Reconfigurable FPGA Calibration Bus Interface Power Requirement Physical Maximum Working Voltage Environmental Operating Environment Storage Environment Shock and Vibration (for NI PXI-783xR Only) Safety Electromagnetic Compatibility CE Compliance B Connecting I/O Signals Appendix B Connecting I/O Signals NI 783xR User Manual B-2 ni.com Figure B-2. NI783xR I/O Connector Pin Assignments NI7 83xR DIO NI 7830R MIO NI 7831R/7833R MIO Caution Connections that exceed any of the maximum ratings of input or output signals Table B-1. I/O Connector Signal Descriptions Connecting to CompactRIO Extension I/O Chassis Table B-2. NI783xR I/O Signal Summary Connecting to 5B and SSR Signal Conditioning Figure B-3. Connector Pinouts when Using NSC68-262650 Cable AO 07 Connector AI 07 Connector DIO 015 Connector Figure B-4. Connector Pinouts when Using the NSC68-5050 Cable DIO 023 Connector DIO 2439 Connector C Using the SCB-68 Shielded Connector Block D 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