Measurement Computing 6224 - Manual (Page 31)

7-6 Strain and Pressure/Force 6224 User’s Manual
Half-Bridge II
Half-bridge type II only measures bending strain.
Half-bridge type II 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 temperature.
Sensitivity at 1000 is ~ 1 mV
out
/ V
EX
input.
The following symbols apply to the above circuit diagram and to the equations provided in the supplemental information.
R1 and R2 are half-bridge completion resistors.
R3 is the active strain-gauge element measuring compressive strain (– ).
R4 is the active strain-gauge element measuring tensile strain (+ ).
Supplemental Information
Data from strain channels (Half-Bridge II) is converted to strain units using the following equation:
10
6
2 V r
GF
1
R L
R g