A digital whole-body vibration exposure recorder for monitoring heavy equipment in the field

A self-contained vibration analyzer for the evaluation of whole-body vibration exposure of heavy equipment operators has been developed, using digital filtering techniques. Two sets of digital filters were designed: a) a set of weighting filters according to the ISO 2631 standard (Guide for the Evaluation of Human Exposure to Whole-body Vibration) b) a set of second order octave band filters covering the range from 1 to 80 Hz. The implementation was based on a low power 8 bit microprocessor, supported by a stack-oriented arithmetic processor. The instrument processes 3 analogue inputs from a triaxial straingage accelerometer and outputs the filtered rms (10 sec) signal for analogue recording. The filters can be selected in the field as either conforming to the ISO 2631 standard or to be 1 of 6 octave filters. The instrument was evaluated in the laboratory and used for field measurements under production conditions in forest harvesting. On the particular machine investigated, it was found that the operator vibration exposure is well below the limits set by the ISO 2631 standard. But high variations in the measured rms vibration levels indicate the presence of a large energy contribution from shock impulses, which are outside the scope of the standard.Applied Science, Faculty ofElectrical and Computer Engineering, Department ofGraduat