Chapter 4
Connecting Signals
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National Instruments Corporation
4-9
setting of the amplifier. The amplifier output voltage is referenced to the
device ground. The device ADC measures this output voltage when it
performs A/D conversions.
Connecting Analog Input Signals
The following sections discuss the use of single-ended and differential
measurements and make recommendations for measuring both floating
and ground-referenced signal sources.
Figure 4-3 summarizes the recommended input configuration for both
types of signal sources.
Figure 4-3.
Summary of AI Connections
Input
Input
Floating Signal Source
(Not Connected to Building Ground)
Grounded Signal Source
Differential
(DIFF)
Single-Ended —
Nonreferenced
(NRSE)
Examples
• Ungrounded Thermocouples
• Signal Conditioning with
Isolated Outputs
• Battery Devices
Example
• Plug-in Instruments with Nonisolated
Outputs
+
–
+
–
V
1
ACH
AISENSE
AIGND
+
–
+
–
V
1
ACH(+)
ACH(–)
AIGND
+
–
+
–
V
1
ACH(+)
ACH(–)
AIGND
R
See text for information on bias resistors.
+
–
+
–
V
1
ACH
AISENSE
AIGND
R
