©
National Instruments Corp.
13
NI 9237 Operating Instructions and Specifications
The act
u
al bridge excitation voltage is smaller than the voltage at
the EX+ and EX– leads. If yo
u
do not
u
se remote sensing of the
act
u
al bridge voltage, the res
u
lting gain error is:
for half-bridge sensors and
for f
u
ll-bridge sensors.
If yo
u
connect the remote sense signals directly to the bridge
resistors, the NI 9237 senses the act
u
al bridge voltage and
eliminates the gain errors ca
u
sed by the resistance of the EX+ and
EX– leads.
Shunt Calibration
Sh
u
nt calibration can correct for errors from the resistance of both
the excitation wiring and wiring in the individ
u
al resistors of the
bridge. Remote sensing corrects for resistances from the EX pins
on the NI 9237 to the sensor, and sh
u
nt calibration corrects for
these errors and for errors ca
u
sed by wire resistance within an arm
of the bridge. Sh
u
nt calibration is most
u
sef
u
l with q
u
arter-bridge
R
lead
R
bridge
-----------------
2
R
lead
⋅
R
bridge
--------------------
