Dataforth Application Note: Strain Gage Signal Conditioner
May 2018,
MARIETTA, GA ~
Preamble
Examining all types of individual strain gage element configurations is beyond the scope of this application note; however, the behavior fundamentals of strain gages interfaced to Dataforth’s strain gage bridge signal conditioning modules will be examined. The effects of line resistance, strain gage parameter tolerances, and methods of excitation are included.
This application note is based on the basic bridge circuit fundamentals published in Dataforth’s Application Note AN117 “Basic Bridge Circuits,” which should be considered prerequisite reading; see Reference 1.
Review Conductive Resistance
The expression for resistance, Equation 2, shows that conductive resistance depends on geometry (length and area) and the molecular structure quantities: “n,” density of electrons available for motion; “q,” charge of an electron, and “ì ,” mobility of electrons. Electron charge “q” is constant; “free” electrons “n” are dependent upon temperature and internal molecular structure, and mobility “ì ,” the relative ease with which electrons can navigate through a molecular structure, is very sensitive to temperature, material composition, and structure deformity. Mathematically (a little calculus here), the change in conductive resistance is described in Equation 3, which again says resistance change is a function of both geometry and electron behavior.
Basic Strain Gage
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