©
National Instruments Corporation
35
SCC-SG Series Strain-Gauge Modules User Guide
Figure 27.
Full-Bridge Shunt Calibration Configuration Using SCC-SG11
and SCC-SG04/24 (One Channel) to Shunt R
4
Each screw terminal of the SCC-SG11 is labeled by pin number <1..4>.
The SCC-SG11 contains two shunt-calibration circuits, each consisting of
a precision 301 k
Ω
resistor and a relay contact. The circuits are independent
of each other, but the relay contacts are controlled together by DAQ device
digital output channel DIO(
X
). The value of
X
is determined by the number
of the SC-2345 socket, J(
X
+9), where you plug in the SCC-SG11.
When DIO(
X
) is set to 1 on the DAQ device, the shunt-calibration circuits
are enabled and the LED indicator on the SCC-SG11 is lit. When DIO(
X
)
is set to 0, the circuits are disabled and the LED indicator on the SCC-SG11
is off. At startup or reset, the circuits are disabled. When the circuits are
enabled, the shunt-calibration resistor is connected to the SCC-SG11 screw
terminals. This allows you to place a resistor in parallel with a strain-gauge
element.
Note
Shunt calibration with the SCC-SG11 is not a dual-stage configuration. You must
supply additional wires as described in this section and shown in Figures 25, 26, and 27.
1
The SCC-SG24 provides a 10 VDC excitation current.
DAQ Device
ACH(
X
)
SCC-SG04/24
x 100
2.5 V
1
+
–
ACH(
X
)+
ACH(
X
)–
V
EX
+
V
EX
–
SCC-SG11
R
SCAL
DIO(
X
)
3
4
1
2
Full-Bridge
R
3
R
4
R
2
R
1
