National Instruments SCXI-1121 - Manual (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 k
Ω
. 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
Figure 2-9 for visual help):
where
R
g
is the nominal strain-gauge resistance value.
R
d
is either a completion resistor or a second strain-gauge nominal
resistance.
R
null
is the nulling resistor value.
V
exc
is the excitation voltage (3.333 or 10 V).
For example, assuming:
V
exc
= 3.333 V
R
g
= 120
Ω
R
d
= 120
Ω
R
null
= 39 k
Ω
V
nulling
= ±2.56 mV
Table 2-11. Nulling Resistors and Corresponding Channel
Channel Number Nulling Resistor
0 R3
1 R5
2 R7
3 R9
V
nullingrange
V
exc
2
----------
V
exc
R
d
R
null
R
g
+
( )
R
null
R
g
R
d
R
null
R
g
+
( )
+
----------------------------------------------------------- –
±
=