Base strain effects on force measurements

Force transducers directly interact with their environment. In this study, a force transducer is attached to the midpoint of a free-free beam and is used to measure the force on a rigid mass that vibrates with the beam. The ratio of force to mass times acceleration is measured for several different masses over a frequency range that includes the first four odd natural frequencies of the beam. Then the force transducer is mounted so that the beam's strain is isolated from the transducer. The tests are repeated. The results dramatically illustrate the effects of base strain on the force measurements. A simple theoretical model is developed that explains the vertical axis shift in the calibration curve. Paper was presented at SEM 1994 Spring Conference and Exhibits.