Design and testing of [a] vibratory force measurement system for hand-arm vibration applications

This study involves design and testing of a measurement system that effectively measures the force transmitted to various points on the finger of the worker's hand without altering the true working conditions.

Hand Arm Vibration Syndrome (HAYS) was first recognized in the early twentieth century. HAYS has been recognized [as] a major risk factor for workers using vibrating tools in a cold environment. Three hand-arm vibration standards have been developed to assess the risk involved in the usage of vibrating tools in the United States: ISO 5349, ACGIH-TLY and ANSI S3.34. These standards use the acceleration level measured directly on the vibrating surface as their reference criteria. This may not be sufficient to assess the risk of vibration exposure because coupling conditions at contact surface of the tools, such as grip force and feed force, are not considered with these standards.

An alternative method of assessing the vibration exposure involves the measurement of the force transmitted to the hand during the operation of the tools. Previously, a system was developed for measuring the force through the use of piezoelectric force transducers. Because of the characteristics of the transducer, static force measurements were not possible. Also due to its physical dimensions, simulation of true working conditions may not have been possible.

For this study, a thin film resistive force sensor, having negligible thickness, was selected and supporting electronics were developed. The system was calibrated using  static and dynamic force input. Effects of electromagnetic interference were investigated. The system was also tested for its effectiveness by measuring the force from an electric drill while varying the feed force of the tool. The results show that reliable and accurate force measurements can be made between 0 Hz to 1600Hz without altering the normal working conditions.