Mechanical analysis of normal force interference on axial force measurement for internal sting balance

For an internal sting balance, the measurement elements of axial force are independent from the measurement elements of other loads. The interference of other loads causes errors in axial force measurement. The existing way to compensate these errors is to perform balance calibration which is basically a mathematical method without mechanical meaning. In this paper, a mechanical analysis is performed to reveal how the normal force causes errors in axial force measurement, based on which a modified Wheatstone bridge equation is presented to serve as an alternative calibration method. Results of case studies show that the presented modified Wheatstone bridge equation can effectively reduce the interference error of normal force on the axial force measurement.