ADLINK USB-1210 - Manual (Page 23)

Introduction 13
USB-1210
devices that plug into the existing power systems are
ground-referenced signal sources.
Input Configurations
Differential Input Mode
Differential input mode provides positive signal and negative
signal inputs that respond to signal voltage difference between
them, as shown. If the signal source is ground-referenced, dif-
ferential mode can be used for noise rejection for improvement
over single-ended mode.
Figure 1-10: GRND-Referenced Source w/ DIFF Input
Connection of a floating signal source to the USB-1210 module
in differential input mode is further shown. For floating signal
sources, the negative side of the signal should be connected to
the AIGND, with less noise coupled into the signal connections
than in single-end mode.
Figure 1-11: Floating Source w/ DIFF Input
AIxH
AIxL
x = 0, ..., 3
Ground
referenced
signal source
To A/D
converter
IGND
+
-
Instrumentation amplifier
V
cm
Common-mode
noise & Ground
potential
+
-
Input multiplexer
AIxH
AIxL
x = 0, ..., 3
+ To A/D
Converter
IGND
+
-
-
Instrumentation
Amplifier
Input Multiplexer
Floating
Signal
Source