Measurement Computing 6224 - Manual (Page 33)

7-8 Strain and Pressure/Force 6224 User’s Manual
Full-Bridge II
Full-bridge type II only measures bending strain.
Full-bridge type II configuration has the following characteristics:
Four active strain-gauge elements. Two are mounted in the direction of bending strain with one on one side of the
strain specimen (top), the other on the opposite side (bottom). The other two act together as a Poisson gauge and are
mounted transverse (perpendicular) to the principal axis of strain with one on one side of the strain specimen (top),
the other on the opposite side (bottom).
Rejects axial strain.
Compensates for temperature.
Compensates for the aggregate effect on the principle strain measurement due to the Poisson’s ratio of the specimen
material.
Compensates for lead resistance.
Sensitivity at 1000 is ~ 1.3 mV
out
/ V
EX
input.
The following symbols apply to the above circuit diagram and to the equations provided in the supplemental information.
R1 is an active strain-gauge element measuring compressive Poisson effect (– ).
R2 is an active strain-gauge element measuring tensile Poisson effect (+ ).
R3 is an active strain-gauge element measuring compressive strain (– ).
R4 is an active strain-gauge element measuring tensile strain (+ ).
Supplemental Information
Data from strain channels (Full-Bridge II) is converted to strain units using the following equation:
10
6
2 V r
GF 1 ( )