Significant, repeatable errors can result when loading off-the-shelf 6-component force transducers at relatively short distances off-axis. The availability of low-cost high-precision 6-component force transducers has resulted in their wide adoption in aerodynamic testing of small unmanned aircraft and their propulsion systems. Companies such as ATI Industrial Automation (www.ati-ia.com) offer a comprehensive range of force transducers. These transducers are robust, have excellent overload protection, provide good frequency response, weak temperature sensitivity (and integral compensation), are available with an array of different interface options (Ethernet, Differential Voltage), have NIST traceable calibrations, and many are available in waterproof form. For the most part, these sensors have evolved from sensing elements in robotic end-effectors and as such are extremely accurate when the applied loads are in close proximity to the sensor face and axially aligned with the transducer center.
This paper will describe an instance where such axial alignment is not possible. The endeavor of loading the sensor off of the balance center resulted in error in force and significant error in torque. As a result, a number of permutations of off-axis loading were investigated to better elucidate the cause of the error. The magnitude of the measurement error provides substantial incentive to produce an independent sensor interaction matrix when test circumstances dictate similar off balance center loading.
Available at: http://works.bepress.com/aaron-altman/16/