DASYLab Addon Module: 'ISO8041' Human Response to Vibrations

• Analysis of whole body vibrations and hand-arm vibrations
• Required by the work safety directive EU 2002/44
• Analysis of whole body vibrations, head vibrations and hand-arm vibrations
• Standard-compliant filtering and processing of the recorded vibration signals
• Derived values such as the crest factor, the vibration dose, the maximum values
• Auto calibration function for the connected sensors
  

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The new DASYLab application module comprises of a complete analysis of the impact of vibrations on the human body. The module was developed in compliance with the EU directive 2002/44 and meets the requirements for DIN/ISO 8041 and VDI 2057 directive. The directives states minimum rules to protect the health and safety of workers from hazardous vibrations. According to the directive, the vibration behaviour of machines, which generate vibrations the human body is exposed to, must be measured and limited. The directive differentiates between whole body vibrations, hand-arm vibrations and different vibration frequencies. For example, "Sea sickness" is caused by extremely slow whole body vibrations. DASYLab calculates the recorded vibrations with digital filters according to all required evaluation specifications:

• Wb Vertical whole body vibration of a seated, standing, or recumbent person (ISO 2631-4)
• WC Horizontal whole body vibration, x-axis, seated person (ISO 2631-1)
• Wd Horizontal whole body vibration, x or y-axis, seated, standing or recumbent person (ISO 2631-1)
• We Rotational whole body vibration, all directions, seated person (ISO 2631-1)
• Wf Low frequency vertical whole body vibration, z-axis, sea sickness, kinetic effect on a seated or standing person (ISO 2631-1)
• Wh Hand-arm vibrations, all directions (ISO 5349-1)
• Wj Vertical head vibration, x-axis, recumbent person (ISO 2631-1)
• Wk Vertical whole body vibrations of a seated, standing or recumbent person (ISO 2631-1)
• Wm Whole body vibration in buildings, all directions (ISO 2631-2)

Standards met:
EN ISO 8041 (2004)
EN ISO 5349 (2001)
EN ISO 2631
DIN 45 675 (1987)
VDI directive VDI 2057 (2002)
EU directive 2002/44/EG

EN 1032 (2003) Mechanical vibration - Testing mobile machinery on order to determine the vibration emission value
EN 13059 (2002) Saftey of industrial trucks - Test methods for measuring vibration

Necessary scan rates:
Digital filters only can calculate correctly up to just under half the scan rate. If the scan rate is too low, additional scan rates are interpolated in order to simulate a sufficient scan rate. The maximum interpolation factor is 8. If the interpolation factor needs to be higher, a warning message appears when the module starts.
Note, if the scan rates are too low, the accuracy for higher signal frequencies is impaired:

Required hardware properties

Number of channels
For most applications three for the three axes x, y, z, or a multiple of three when several measurement points are acquired in one measurement.

Scan rate
For most human vibration tests a scan rate of 1 kHz per channel is enough but for hand-arm vibrations 10 kHz is required (see also accuracy and necessary scan rates). If the scan rates are low, the DASYLab add-on module ISO8041 interpolates the input signal and the accuracy for higher signal frequencies is reduced.

Lower limit frequency
The ISO 8041 standard dictates filter properties and tolerance spectrums which the DASYLab add-on module ISO8041 meets. If the signal frequencies are very low, the valid tolerances expand.
If the frequencies are low, the sensor and if used the pre-amplifier, the impedance convertor, or the power supply must not exceed the following attenuation:

Sensors
The selection of the acceleration sensors depends largely on the required lower limit frequency.
Sensors with a ICP® supply are a low cost way to measure hand-arm vibrations. The lower limit frequency of ICP® sensors and ICP® supply is often too high for whole body vibrations.
In these cases a loading amplifier is required or sensors that do not work with piezo-electric affects (for example, piezoresistive, DMS, or inductive technology).

ICP® supply
ICP® sensors are supplied with a constant current source. This results in a DC voltage offset, which must be decoupled to receive a lower limit frequency of the ICP® supply.
The measurement device should support ICP® sensors where possible or a separate ICP® supply must be used. In both cases you should adhere to the lower limit frequency the producer specifies.