National Instruments DAQ Series User Manual

Chapter 3 Connecting Signals
© National Instruments Corporation 3-7 DAQCard-700 User Manual
Recommended Input Configurations
The following sections discuss the use of RSE and DIFF measurements and
considerations for measuring both floating and ground-referenced signal
sources. Table 3-1 summarizes the recommended input configurations for
both signal source types.
Single-Ended Connection Considerations
Single-ended connections are those in which all DAQCard-700 AI signals
are referenced to one common ground. The input signals are tied to the
positive input of an operational amplifier that is referenced to the common
ground point.
When the DAQCard-700 is configured for RSE input mode, 16 AI channels
are available. You can use single-ended input connections when the
following criteria are met by all input signals:
• Input signals are high level (greater than 1 V).
• Leads connecting the signals to the DAQCard-700 are less than 15 ft.
• All input signals share a common reference signal (at the source).
If any of the preceding criteria are not met, use the DIFF input mode.
The RSE input mode is referenced, but you can use this mode for
nonreferenced signal sources. In addition, if the computer using the
Table 3-1. Recommended Input Configurations for Ground-Referenced and Floating Measurement Systems
System Type Type of Signal
Recommended Input
Configurations
Ground-referenced system,
such as a desktop computer
Ground referenced
(nonisolated outputs,
plug-in instruments)
DIFF
Floating
(batteries, thermocouples,
isolated outputs)
DIFF with bias resistors
RSE
Floating system, such as a
battery-powered computer
Ground referenced
(nonisolated outputs,
plug-in instruments)
DIFF with bias resistors
RSE
Floating
(batteries, thermocouples,
isolated outputs)
DIFF with bias resistors
RSE

National Instruments DAQ Series Specifications

General

Brand	National Instruments
Model	DAQ Series
Category	Recording Equipment
Language	English