National Instruments SCXI-1321 - Manual (Page 9)

© National Instruments Corporation 9 SCXI-1321 Terminal Block Installation Guide
The factory default value of all the nulling resistors on the terminal block
is 39 k
Ω .
Note These resistors are socketed for easy replacement. These sockets best fit a 1/4 W
resistor lead size.
To determine the nulling range, use the following formula while referring
to Figures 3 through 5:
where
V
exc
is the excitation voltage (3.3 V or 10 V)
R
d
is either a completion resistor or a second strain-gauge nominal
resistance
R
null
is the nulling resistor value
(range of trim potentiometer + nulling resistor)
R
g
is the nominal strain-gauge resistance value
For example,
V
nulling range
= ±2.56 mV
V
exc
= 3.3 V
R
d
= 120
Ω
R
null
= 39 k
Ω
R
g
= 120
Ω
Table 2. Nulling Resistors and Corresponding Channels
Channel Number Nulling Resistor
0 R3
1 R5
2 R7
3 R9
V
nulling range
V
exc
2
----------
V
exc
R
d
R
null
R
g
+
( )
R
null
R
g
R
d
R
null
R
g
+
( )
+
----------------------------------------------------------- –
±
=