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3.2
Analog Input Signal Connection
The PCI-9113A provides 32 single-ended or 16 different analog input
signals which can be converted to digital value by the A/D converter. To
avoid ground loops and get more accurate measurement of A/D
conversion, it is quite important to understand the signal source type.
The single-ended mode has only one input relative to ground and is
suitable for connecting with the floating signal source. The floating
source means it does not have any connection to real ground. Figure 3.3
shows the single-ended connection. Note that when more than two
floating sources are connected, the sources must be with common
ground.
Signal
Source
V1
Figure 3.3: Signal sources and single-ended connection
The differential input (DI) mode means the voltage signal to be
measured is by a pair of signals, for example, AI3L and AI3H is a
differential pair. The AD circuits measure the voltage difference between
the differential pair. The common mode noise can be reduced under this
mode. Note that the differential signal pair should be still common
ground to the isolation ground plane. Figure 3.4 shows the differential
analog signal input connection.
G r o u n d
Signal
S o u r c e
Figure 3.4: Grounded source and differential input
AIn
...
V2
IGND
n = 0, ...,31
x = 0, ..., 15
V c m = V G 1 - V G 2
V G 1
Input Multipexer
AIxH
AIxL
I G N D
Opertional
Amplifier
To A/D
To A/D
+
-
V G 2
Signal Connections 15
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