Chapter 2
Using the Module
©
National Instruments Corporation
2-13
Figure 2-12.
Full-Bridge Type I Circuit Diagram
The following symbols apply to the circuit diagram and equations:
•
R
1
—Active element measuring compressive strain (–
ε
).
•
R
2
—Active element measuring tensile strain (+
ε
).
•
R
3
—Active element measuring compressive strain (–
ε
).
•
R
4
—Active element measuring tensile strain (+
ε
).
•
R
s
— Shunt calibration resistor located inside the NI PXIe-4330/4331.
•
R
L
—Lead resistance.
•
GF
—Gage Factor, specified by the gage manufacturer.
•
V
CH
—Measured voltage of the bridge.
•
V
EX
—Excitation voltage provided by the NI PXIe-4330/4331.
•
V
r
—Offset compensated ratiometric bridge output defined by the following equation:
Note
The ratio of the bridge output voltage and the excitation voltage is done internally
on the NI PXIe-4330/4331.
+
–
+
–
AI +
RS+
EX+
R
1
R
2
R
4
R
3
RS–
QTR
/SC
Shunt
Cal A
+
–
+
–
R
L
R
L
PXIe-4330/4331 Set Bridge
Configuration to Full Bridge
TB-4330
Transducer
V
CH
R
L
R
L
R
L
EX–
AI–
V
EX
R
S
V
r
V
CH
strained
(
)
V
CH
unstrained
(
)
–
V
EX
---------------------------------------------------------------------------------
=
