National Instruments SCXI-1321 Installation Manual page 13

© National Instruments Corporation
z is the module slot of the SCXI-1121
w is the channel of the module that you want to engage the shunt and
take measurements
For example, if you want to measure the voltage at channel 0 with the shunt
resistor enabled, use the SCXI channel string
ob0 ! sc1 ! md1 ! shunt0
You also can specify a list of channels by using
ob0 ! sc1 ! md1 ! shunt0: w
Measurements Manual for information on using SCXI channel strings.
The shunting resistors R
a resistor of another value to achieve the required nulling range for your
application. The sockets and corresponding channels are shown in Table 3.
The factory installed R
±1% value.
Table 3. Socket to Channel Relationship
Channel
0
1
2
3
Assuming a quarter-bridge strain-gauge configuration with a gauge factor
of GF = 2, the equivalent strain change introduced by the R
resistor is –199 µε.
Refer to the Traditional NI-DAQ User Manual for more information on
strain-gauge bridge configurations and formulas.
Use the following formula to determine the change due to this shunting
resistor:
V
change
Next, using the appropriate strain-gauge strain formula, and assuming that
you have no static voltage, determine the equivalent strain the R
provide. For example, R
.
, for example. Refer to the LabVIEW
are socketed so that you can replace them with
SCAL
provided on the terminal block have a 301 kΩ
SCAL
Shunt Resistor Socket
(
V R R
+
ex d SCAL
= ---------------------------------------------------------------- -
(
R R R R
+
g d SCAL
SCAL
= 301 kΩ and a quarter-bridge 120 Ω strain
SCAL
13 SCXI-1321 Terminal Block Installation Guide
R4
R6
R8
R10
shunting
SCAL
)
R V
g ex
– -------
)
R 2
+
g
should
SCAL