AS ISO 5349.2:2013 pdf download – Mechanical vibration – Measurement and evaluation of human exposure to hand-transmitted vibration
6.1.2.2 Vibration magnitude
Hand-held machines can produce high vibration magnitudes. A pneumatic hammer, for example, may generate a maximum acceleration of 20000 m/s² to 50000 m/s². However, much of this energy is at frequencies well outside the frequency range used in this part of ISO 5349. The accelerometer chosen for the measurement has therefore to be able to operate at these very high vibration magnitudes and yet still respond to the much lower magnitudes in the frequency range from 6,3 Hz to 1 250 Hz (one-third-octave band mid-frequencies). For the use of mechanical filters to suppress vibration at very high frequencies, see annex C.
6.1.2.3 Frequency range
Accelerometer selection will also be influenced by the fundamental resonance frequency of the accelerometer, this is a characteristic of the accelerometer (it is sometimes referred to as the “mounted resonance frequency”, “natural frequency” or “resonance frequency”). Information on the fundamental resonance frequency will be available from the accelerometer manufacturer. ISO 5348 recommends that the fundamental resonance frequency should be more than five times the maximum frequency of interest (for hand-transmitted vibration, this corresponds to 6250 Hz). For piezoelectric accelerometers, the fundamental resonance frequency should normally be much higher, ideally greater than 30 kHz, to minimize the likelihood of DC-shift distortion (see 6.2.4). NOTE The fundamental resonance frequency of the accelerometer should not be confused with the resonance frequency of the accelerometer when mounted on a hand-held workpiece or power tool which is a characteristic of the whole accelerometer mounting system. In practice, the resonance of the mounted accelerometer on a hand-held workpiece or power tool will be substantially lower than the fundamental resonance frequency (see 6.1.4).
6.1.3 Location of accelerometers
Vibration measurements in accordance with ISO 5349-1 should be made at or near the surface of the hand (or hands) where the vibration enters the body. Preferably, the accelerometer should be located at the middle of the gripping zone (e.g. halfway along the width of the hand when gripping a power tool handle), it is at this location that the most representative evaluation of the vibration entering the hand is obtained. However, it is generally not possible to locate transducers at this point; the transducers will interfere with the normal grip used by the operator. Measurements directly under the hand are usually only possible using special mounting adaptors (see annex D). Such adaptors should fit under the hand, or between the fingers. For most practical measurements, the accelerometers are mounted either side of the hand or on the underside of the tool handle adjacent to the middle of the hand. With adaptors which fit between the fingers, the transducers should be mounted as close as possible to the surface of the tool handle to minimize amplification of rotational vibration components. They should not have any structural resonances which would affect the measured vibration. It is possible to get differences in vibration measurement across the width of the hand, particularly for hand-held power tools with side handles, such as angle grinders, and especially where these handles are flexibly mounted. In these cases it is recommended that two accelerometers positions are used, located at the sides of the hand; the average of the two vibration measurements is then used to estimate vibration exposure. For many hand-held power tools, specific measurement locations and axes have been defined for the measurement of vibration emission by ISO 8662 and other International Standards; these measurement locations are summarized in annex A as examples of measurement locations.