BASE STRAIN EFFECTS ON FORCE MEASUREMENTS

Force transducers directly interact with their environment. In this st udy, a force transducer is attached to the midpoint of a free-free bea m 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 fo r several different masses over a frequency range that includes the fi rst four odd natural frequencies of the beam, Then the force transduce r is mounted so that the beam's strain is isolated from the transducer . The tests are repeated. The results dramatically illustrate the effe cts of base strain on the force measurements. A simple theoretical mod el is developed that explains the vertical axis shift in the calibrati on curve.