Vibration Intensity
Post Analyzer is capable of processing signals related to Vibration Intensity testing. This feature is based on five different vibration testing standards:
Whole Body Vibration – ISO 2631 – 1:1997
Hand-Arm Vibration – ISO 5349 - 1:2001
Building Vibration – ISO 2631 – 2:2003
Building Vibration – BS 6472 – 1:2008
Ship Cabin Vibration – ISO 6954:2001
Measure vibration intensity
The relevant signals generated by Post Analyzer are Weighted RMS Acceleration, Fourth Power Vibration Dose, Running RMS, Maximum Transient Vibration, and the Crest Factor. These signals are generated in all the standards listed above. However, the weighting filter applied to the time waveforms varies by standard.
Basics
The weighted RMS of these data sets is required for evaluation and is calculated by Post Analyzer according to the following equation:
Where aw (t) is the weighted acceleration as a function of time, and T is the duration of the measurement periods.
The fourth power vibration dose value is calculated similarly to the weighted RMS but uses the fourth power instead of the second, making it more sensitive to peaks in the acceleration data sets. Post Analyzer uses the following equation for this calculation:
The Running RMS value is important in cases where transient vibration and shocks are present. These cases can be accounted for by using a small integration time constant. Post Analyzer uses the following equation for this calculation:
Where τ is the integration time constant for running averaging, and to is the observation time.
With the Running RMS values known, the Maximum Transient Vibration Value is simply computed with the following function:
The Crest Factor is defined as the absolute value of the ratio between the maximum instantaneous peak and the RMS for an acceleration signal. Post Analyzer performs this calculation for each frame of processed data.
Post Analyzer is preconfigured to calculate the RMS, Fourth Power Vibration Dose, Running RMS, Maximum Transient Vibration Value, and Crest Factor for all Vibration Intensity tests. These signals will be computed for each axis of acquired acceleration data, and can be found in the Measured Signals tab.