©
National Instruments Corporation
11
SCC-SG Series Strain-Gauge Modules User Guide
Figure 5.
SCC-SG01/02 Quarter-Bridge Configuration Connection (Two Channels)
Connect the two-wire strain gauge element leads to ACH(
X
) and V
EX
+. For
a three-wire strain gauge, connect the two-wire lead to ACH(
X
)+ and R(
X
),
then connect the single lead to V
EX
+. Figure 5 shows two quarter-bridge
configurations using ACH(
X
) and ACH(
X
+8) with a three-wire strain
gauge connected to ACH(
X
) and a two-wire strain gauge connected to
ACH(
X
+8). If you are using a two-wire strain gauge, short the ACH(
X
) or
ACH(
X
+8) screw terminal with the corresponding reference screw
terminal, R(
X
) and R(
X
+8).
The dummy resistor must be equal in value to the nominal resistance of the
active strain-gauge element. The SCC-SG01 contains one 120
Ω
quarter-bridge completion resistor per channel. The SCC-SG02 contains
one 350
Ω
quarter-bridge completion resistor per channel. One socketed
quarter-bridge completion resistor is internally connected between R(
X
)
and analog ground. The other is between R(
X
+8) and analog ground. These
R
4
Strain-Gauge Active Element
R
3
Quarter-Bridge Completion Resistor
R
NULL
Nulling Resistor
ACH(
X
)+
V
EX
+
Reserved
ACH(
X
+8)+
R(
X
)
Trimming
Potentiometer
+
–
R
NULL
Trimming
Potentiometer
Half-Bridge
Completion
Reference
2.5 V
+
–
R
NULL
R
3
R
3
2.5 V
R(
X
+8)
6
5
4
3
2
1
Analog Ground
R
4
Three-Wire
R
4
Two-Wire
2.5 V
2.5 V
Half-Bridge
Completion
Reference
2.5 V
