A novel instrumented ring for the measurement of grip force adjustments during precision grip tasks

A wide range of scientific and clinical research studies use the measurement of grip force to quantify hand function and activities during daily living. Many applications of instrumented objects can be found in the biomechanical and neurophysiological literature. However, these were found not to be suitable for the measurement of grip force and force modulations during precision grip independently from the hand orientation. The low-cost precision grip force transducer described here is capable of recording magnitude, direction and modulation of the force exerted on a closed ring. The design is based on a standard proving ring, onto which a second set of strain gauges is applied. The outputs of both Wheatstone bridges yield a unique signature for every position under a two-point load. The tested aluminium ring had an outer diameter of 83 mm, a wall thickness of 3 mm and a height of 12 mm. With eight single bending strain gauges used, the maximum load was 100 N. During a grip task, tremor components from d.c. to 45 Hz could be detected. The newly developed ring might therefore find a use in many biomechanical and neurophysiological studies as a tool for measuring grip force and its fine modulations.