Chapter 2
Using the Module
©
National Instruments Corporation
2-15
Figure 2-14.
Full-Bridge Type II Circuit Diagram
The following symbols apply to the circuit diagram and equations:
•
R
1
—Active element measuring compressive Poisson effect (–
νε
).
•
R
2
—Active element measuring tensile Poisson effect (+
νε
).
•
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.
•
ν
—Poisson’s ratio, defined as the negative ratio of transverse strain to axial strain
(longitudinal) strain. Poisson’s ratio is a material property of the specimen you are
measuring.
•
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:
+
–
+
–
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
+
v
V
r
V
CH
strained
(
)
V
CH
unstrained
(
)
–
V
EX
---------------------------------------------------------------------------------
=
