Signal Connections Chapter 3
Lab-PC+ User Manual 3-8 © National Instruments Corporation
+
-
+
Grounded
Signal
Source
V
m
Measured
Voltage
-
V
s
-
+
I/O Connector Lab-PC+ Board in DIFF Configuration
1
3
5
7
2
4
6
8
9
Common
Mode
Noise,
Ground
Potential,
and so on
ACH 0
AGND
11
AISENSE/AIGND
ACH 2
ACH 4
ACH 6
ACH 1
ACH 3
ACH 5
ACH 7
(not connected)
V
cm
-
+

Figure 3-3. Differential Input Connections for Grounded Signal Sources

With this type of connection, the instrumentation amplifier rejects both the common mode noise

in the signal and the ground potential difference between the signal source and the Lab-PC+

ground (shown as Vcm in Figure 3-3).

Differential Connections for Floating Signal Sources

Figure 3-4 shows how to connect a floating signal source to a Lab-PC+ board configured for

DIFF input. Configuration instructions are included under Analog Input Configuration in

Chapter 2, Configuration and Installation.