The Fluidic Load Cell

A possible fluidic load cell design consists of three parts: a structural member that deforms linearly with load, a fluidic strain gage having fluidic resistance that changes with deformation, and a three-stage laminar proportional amplifier-gain block that amplifies the change in strain gage through-flow to useful levels. This Technical Brief presents design relations for the first two parts of such a system. Two compressive load cells were built, incorporating different fabrication techniques and deformation-sensing methods. The loading range of these cells is about 0 to 20 kN (0 to 2 tons) with a dynamic range greater than 100 and a typical full-scale output pressure of 30 pascals (4 × 10⁻³ psi). Possible applications for fluidic load cells include force measurements in highly incendiary or radiative environments and/or when other fluid control circuitry is used.