NuDAQ ACL-8112 Series, Руководство пользователя

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Signal Connections
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of A/D conversion, it is quite important to understand the signal source
type and how to choose the analog input modes: signal-ended and
differential. The ACL-8112 offers jumpers to select 16 single-ended or 8
different analog inputs.
Single-ended Mode:
The single-ended mode has only one input relative to ground and it
suitable for connecting with the
floating signal source . The floating source
means it does not have any connection to ground. Figure 3.4 shows the
single-ended connection. Note that when more than two floating sources
are connected, the sources must be with common ground.
Figure 3.4 Floating source and single-ended
Differential input mode
The differential input mode provides two inputs that respond to the
difference signal between them. If the signal source has one side
connected to local ground, the differential mode can be used for reducing
ground loop. Figure 3.5 shows the connection of the differential input
mode. However, even if the signal source is local grounded, the single-
ended still can be used when the Vcm ( Common Mode Voltage) is very
small and the effect of ground loop can be negated.
AIHn
AILn
n = 0, ..., 8
Ground
Signal
Source
To A/D Converter
VG1 VG2
Vcm = VG1 - VG2
GND
+
-