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 kΩ .
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
Vexc is the excitation voltage (3.3 V or 10 V)
Rd is either a completion resistor or a second strain-gauge nominal
resistance
Rnull is the nulling resistor value
(range of trim potentiometer + nulling resistor)
Rg is the nominal strain-gauge resistance value
For example,
Vnulling range = ±2.56 mV
Vexc = 3.3 V
Rd = 120 Ω
Rnull = 39 kΩ
Rg = 120 Ω
Table 2. Nulling Resistors and Corresponding Channels
Channel Number Nulling Resistor
0R3
1R5
2R7
3R9
Vnulling range
Vexc
2
----------VexcRdRnull Rg
+()
RnullRgRdRnull Rg
+()+
-----------------------------------------------------------–±=