Strain gauge types explained – Measurement Computing 6224 User Manual

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7-2 Strain and Pressure/Force

6224 User’s Manual

Strain Gauge Types Explained

This section uses figures to represent axial and/or bending strain to indicate the type(s) of strain that applies to a
given bridge type. It also provides simple schematics. For each type of bridge, supplemental information shows
two equations: the first is the equation used to convert voltage to strain; the second is an equation you can use to
simulate the effect on strain by applying a shunt resistor across R3. In the upcoming figures and equations,
acronyms, formulas, and variables are defined as:

is the measured strain (+ is tensile strain and -

is compressive strain).

is the simulated strain.

GF is the Gauge Factor, which should be specified by the gauge manufacturer.

is the nominal gauge resistance, which should be specified by the gauge manufacturer.

is the lead resistance. If lead lengths are long, R

can significantly impact measurement accuracy.

is the shunt calibration resistor value.

U is the ratio of expected signal voltage to excitation voltage with the shunt calibration circuit engaged.
Parameter U appears in the equations for simulated strain and is defined by the following equation:

is the Poisson’s ratio, defined as the negative ratio of transverse strain to axial strain (longitudinal) strain.

is the measured signal’s voltage.

is the excitation voltage.

is the voltage ratio that is used in the voltage to strain conversion equations and is defined by the

following equation:

(strained)

(unstrained)