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National Instruments E Series Types of Signal Sources, Input Configurations,

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Chapter 4 Signal Connections

DAQCard E Series User Manual 4-12

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National Instruments Corporation

Types of Signal Sources

When configuring the input channels and making signal connections,

you must first determine whether the signal sources are floating or

ground-referenced. The following sections describe these two types of

signals.

Floating Signal Sources

A floating signal source is one that is not connected in any way to the

building ground system but, rather, has an isolated ground-reference

point. Some examples of floating signal sources are outputs of

transformers, thermocouples, battery-powered devices, optical isolator

output, and isolation amplifiers. An instrument or device that has an

isolated output is a floating signal source. You must tie the ground

reference of a floating signal to your DAQCard analog input ground to

establish a local or onboard reference for the signal. Otherwise, the

measured input signal varies as the source floats out of the

common-mode input range.

Ground-Referenced Signal Sources

A ground-referenced signal source is one that is connected in some

way to the building system ground and is, therefore, already connected

to a common ground point with respect to the DAQCard, assuming that

the computer is plugged into the same power system. Nonisolated

output of instruments and devices that plug into the building power

system falls into this category.

The difference in ground potential between two instruments connected

to the same building power system is typically between 1 and 100 mV

but can be much higher if power distribution circuits are not properly

connected. If a grounded signal source is improperly measured, this

difference may appear as an error in the measurement. The connection

instructions for grounded signal sources are designed to eliminate this

ground potential difference from the measured signal.

Input Configurations

You can configure your DAQCard for one of three input modes—

NRSE, RSE, or DIFF. The following sections discuss the use of

single-ended and differential measurements and considerations for

measuring both floating and ground-referenced signal sources.

Contents

Main Page Important Information This document was created with FrameMaker 4.0.4 WARNING REGARDING MEDICAL AND CLINICAL USE OF NATIONAL INSTRUMENTS PRODUCTS Trademarks Page Chapter 4 Signal Connections Page Page Figures Tables About This Manual Organization of This Manual Conventions Used in This Manual National Instruments Documentation Related Documentation Customer Communication Introduction About the DAQCard E Series What You Need to Get Started LabVIEW and LabWindows/CVI Application Software Software Programming Choices NI-DAQ Driver Software Register-Level Programming Optional Equipment Custom Cabling Unpacking Installation and Configuration Installation Configuration Page National Instruments Corporation 3-1 DAQCard E Series User Manual Hardware Overview DAQ - STC This document was created with FrameMaker 4.0.4 I/O Connector Analog Input Input Mode Input Polarity and Input Range Page Page Considerations for Selecting Input Ranges Dither Chapter 3 Hardware Overview National Instruments Corporation 3-7 DAQCard E Series User Manual d. Dither enabled; average of 50 acquisitions c. Dither enabled; no averaging Dither Figure 3-3. Page Analog Trigger Page Page Digital I/O Timing Signal Routing Programmable Function Inputs DAQCard Clocks Many functions performed by the DAQCard E Series cards require a Signal Connections I/O Connector DAQCard E Series User Manual 4-2 Figure 4-1. I/O Connector Pin Assignment for the DAQCard-AI-16E-4 and DAQCard-AI-16XE-50 National Instruments Corporation 4-3 DAQCard E Series User Manual Table 4-1. I/O Connector Signal Descriptions DAQCard E Series User Manual 4-4 Table 4-1. I/O Connector Signal Descriptions (Continued) National Instruments Corporation 4-5 DAQCard E Series User Manual Table 4-2 shows the I/O signal summary for the DAQCard-AI-16E-4. I/O Signal Summary, DAQCard-AI-16E-4 Table 4-2. I/O Signal Summary, DAQCard-AI-16E-4 (Continued) Table 4-2. National Instruments Corporation 4-7 DAQCard E Series User Manual Table 4-2. I/O Signal Summary, DAQCard-AI-16E-4 (Continued) DAQCard E Series User Manual 4-8 Table 4-3 shows the I/O signal summary for the DAQCard-AI-16XE-50. I/O Signal Summary, DAQCard-AI-16XE-50 Table 4-3. Table 4-3. I/O Signal Summary, DAQCard-AI-16XE-50 (Continued) Analog Input Signal Connections Page Types of Signal Sources Input Configurations Ground-Referenced Signal Sources Floating Signal Sources Figure 4-3 summarizes the recommended input configuration for both types of signal sources. Summary of Analog Input Connections Figure 4-3. Differential Connection Considerations (DIFF Input Configuration) National Instruments Corporation 4-15 DAQCard E Series User Manual Differential Connections for Ground-Referenced Signal Sources Differential Input Connections for Ground-Referenced Signals Figure 4-4. in Figure 4-4. Differential Connections for Nonreferenced or Floating Signal Sources Page Single-Ended Connection Considerations Single-Ended Connections for Floating Signal Sources (RSE Configuration) Single-Ended Connections for Grounded Signal Sources (NRSE Configuration) Common-Mode Signal Rejection Considerations Digital I/O Signal Connections Power Connections Timing Connections Page Programmable Function Input Connections Data Acquisition Timing Connections SCANCLK Signal EXTSTROBE* Signal TRIG1 Signal Page TRIG2 Signal STARTSCAN Signal Page Page CONVERT* Signal AIGATE Signal SISOURCE Signal UISOURCE Signal General-Purpose Timing Signal Connections GPCTR0_SOURCE Signal GPCTR0_GATE Signal GPCTR0_OUT Signal GPCTR0_UP_DOWN Signal GPCTR1_SOURCE Signal GPCTR1_GATE Signal GPCTR1_OUT Signal GPCTR1_UP_DOWN Signal FREQ_OUT Signal Field Wiring Considerations Calibration Loading Calibration Constants Self-Calibration External Calibration Other Considerations Specifications A DAQCard-AI-16E-4 Analog Input Input Characteristics Page Transfer Characteristics Dynamic Characteristics Amplifier Characteristics Stability Digital I/O Timing I/O Triggers Analog Trigger Power Requirement (from PCMCIA I/O channel) Digital Trigger Physical Environment DAQCard-AI-16XE-50 Analog Input Input Characteristics Transfer Characteristics Amplifier Characteristics Dynamic Characteristics Stability Digital I/O Timing I/O Page B Appendix B Optional Cable Connector Descriptions DAQCard E Series User Manual B-2 Figure B-1. 68-Pin AI Connector Pin Assignments Appendix B Optional Cable Connector Descriptions 50-Pin AI Connector Pin Assignments Figure B-2. PC Card Questions and Answers C Configuration Operation Resources Page Resource Conflicts Common Questions D General Information Installation and Configuration Analog Input and Output Timing and Digital I/O Page Page Power-Management Modes E Page Customer Communication FTP Support Electronic Services F Bulletin Board Support Fax and Telephone Support Telephone Fax FaxBack Support E-Mail Support (currently U.S. only) Technical Support Form DAQCard E Series Hardware and Software Configuration Form Other Products National Instruments Products Documentation Comment Form Glossary Symbols A C B D E F H G Page P S R T V U W B A Numbers C D E F G I H L P O N Page Q S R Page T