Chapter 4
Theory of Operation
©
National Instruments Corporation
4-11
Half-Bridge Type II
This section provides information for the half-bridge strain-gauge
configuration type II. The half-bridge type II only measures bending strain.
Figure 4-8 shows how to position strain-gauge resistors in a bending
configuration. Figure 4-9 shows the half-bridge type II circuit wiring
diagram.
Figure 4-8.
Half-Bridge Type II Rejecting Axial and Measuring Bending Strain
A half-bridge type II configuration has the following characteristics:
•
Two active strain-gauge elements. One is mounted in the direction of
bending strain on one side of the strain specimen (top), the other is
mounted in the direction of bending strain on the opposite side
(bottom).
•
Completion resistors provide half bridge completion.
•
Sensitive to bending strain.
•
Rejects axial strain.
•
Compensates for specimen temperature variation.
•
Sensitivity at 1000
µε
is
∼
1 mV
out
/
V
EX
input.
Figure 4-9.
Half-Bridge Type II Circuit Diagram
R
3
R
4
R
3
(– )
R
4
(+ )
Axial
Bending
R
1
R
L
R
2
+
–
–
+
V
EX
V
CH
R
4
(+ )
R
3
(– )
R
L
R
L
