Single Arm Active Bridges

A single active arm bridge has one strain gauge, pictured above in position R1, on the Wheatstone bridge. Assuming a voltage-sensitive deflection bridge with all resistances nominally equal, a zero initial output voltage, and small resistance fluctuations, it can be shown that the output voltage will be given by:

(1)

eo is the bridge output voltage,

ei is the bridge excitation voltage,

R1 is the change in resistance of Resistor 1, and

R is the nominal resistance.

It can also be shown that the strain can be related to the ratio of output voltage to excitation voltage by:

(2)     

is the strain to be measured and

F is the gauge factor.