Chapter 2
Using the Module
2-8
ni.com
To convert module readings to strain use the following equation:
Half-Bridge Type I
This section provides information for the half-bridge strain-gage configuration type I. The
half-bridge type I measures either axial or bending strain. Figure 2-7 shows how to position
strain-gage resistors in an axial and bending configurations. Figure 2-8 shows the half-bridge
type I circuit wiring diagram.
Figure 2-7.
Half-Bridge Type I Measuring Axial and Bending Strain
A half-bridge type I has the following characteristics:
•
Two active strain-gage elements. One strain-gage element is mounted in the direction of
axial strain while the other acts as a Poisson gage and is mounted perpendicular to the
principal axis of strain.
•
Half-bridge completion resistors (R
1
and R
2
) are provided by the NI PXIe-4330/4331.
•
Sensitive to both axial and bending strain.
•
Sensitivity ~ 0.65
μ
V/V per
με
, for GF = 2.0.
strain
ε
( )
4
V
r
–
GF
1 2
V
r
+
(
)
-------------------------------
=
(– )
R
4
(+ )
(– )
Axial
Bending
R
3
R
3
R
4
(+ )
