©
National Instruments Corporation
31
SCC-SG Series Strain-Gauge Modules User Guide
Nulling Range Adjustment
The nulling range of the offset-nulling adjustment circuitry for the
SCC-SG0
X
and SCC-SG24 is referred to input (RTI)
1
and given in Table 2.
The nulling range figures assume a 30 k
Ω
nulling resistor and an excitation
voltage of +2.5 VDC for the SCC-SG0
X
and +10 VDC for the SCC-SG24.
Note
The nulling range of the SCC-SG0
X
and SCC-SG24 is dependent on the excitation
voltage, active strain-gauge element value, and the value of the nulling resistor.
You can change the nulling range of the offset-nulling circuitry for each
channel by replacing its nulling resistor with a nulling resistor of another
value. The value of the nulling resistors on the SCC-SG0
X
and SCC-SG24
is 30 k
Ω
. These nulling resistors are socketed for easy replacement. Refer
to the
section for more information on replacing
resistors.
To determine the nulling range, use the following formula while referring
to Figure 28, 29, or 30:
where
R
4
is the nominal active strain-gauge element resistance value.
R
3
is either the value of the quarter-bridge completion resistor or the
nominal resistance of the second active strain-gauge element. Refer to
Figure 28, 29, or 30 to locate the resistor in quarter-, half-, and
full-bridge configurations.
R
NULL
is the value of the nulling resistor.
V
EX
is the excitation voltage.
1
Calculated relative to the input range of the module
Table 2.
SCC-SG0
X
and SCC-SG24 Nulling Ranges
SCC Module
Active Strain Gauge
Element Value
Nulling Range
SCC-SG01
120
Ω
±
2.5 mV
SCC-SG02/03/04
350
Ω
±
6.6 mV
SCC-SG24
350
Ω
±
29 mV
V
NULLING
±
V
EX
2
---------
V
EX
R
3
R
NULL
R
4
+
(
)
R
NULL
R
4
R
3
R
NULL
R
4
+
(
)
+
-------------------------------------------------------------------
–
=
