National Instruments SCXI-1121 - page 42

Chapter 2 Configuration and Installation
SCXI-1121 User Manual 2-26 www.natinst.com
The value of all the nulling resistors on your terminal block is 39 kΩ. Notice
that these resistors are socketed for easy replacement. These sockets best fit
a 1/4 W resistor lead size.
To determine your nulling range, use the following formula (refer to
Figure2 -9 for visu al help):
where
Rg is the nominal strain-gauge resistance value.
Rd is either a completion resistor or a second strain-gauge nominal
resistance.
Rnull is the nulling resistor value.
Vexc is the excitation voltage (3.333 or 10 V).
For example, assuming:
Vexc = 3.333 V
Rg = 120 Ω
Rd = 120 Ω
Rnull = 39 kΩ
Vnulling = ±2.56 mV
Table 2-11. Nulling Resistors and Corresponding Channel
Channel Number Nulling Resistor
0R3
1R5
2R7
3R9
Vnullingrange Vexc
2
----------VexcRdRnull Rg
+()
RnullRgRdRnull Rg
+()+
-----------------------------------------------------------–±=