Measurement Computing 6224 - Manual (Page 28)

6224 User’s Manual Strain and Pressure/Force 7-3
Quarter-Bridge I
Quarter-bridge type I measures either axial or bending strain.
Quarter-bridge type I has the following characteristics:
A single active strain-gauge element is mounted in the principle direction of axial or bending strain.
A passive quarter-bridge completion resistor (dummy resistor) is required in addition to half-bridge completion.
Temperature variation in specimen decreases the accuracy of the measurements.
Sensitivity at 1000 is ~ 0.5 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 the half-bridge completion resistors.
R3 is the quarter-bridge completion resistor (dummy resistor).
R4 is the active strain-gauge element measuring tensile strain (+ ).
Supplemental Information
Data from strain channels (Quarter-Bridge I) is converted to strain units using the following equation:
10
6
4 V r
GF 1 2 V r
1
R L
R g