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Chapter 3
Measuring Vibration
Hand Arm Vibration
It is advisable to validate your instrument prior to, and after taking
measurements using a known vibration source such as the Castle GA606
Vibration Calibrator.
To ensure measurements are as accurate and as repeatable as possible always
ensure that your cable is tightened securely to your accelerometer and that the
accelerometer is mounted as securely and as flush as possible to the vibration
source. The trailing cable of the accelerometer should also be attached to the
vibration source without creating a potential hazard for the operator or other
people.
Where possible always mount the accelerometer as near to the centre of
where the operator holds and grips the vibration source. In reality this is not
always possible and the best compromise must be achieved.
Measurement durations are dependant on the vibration source, and a minimum
period of 30 seconds for Hand Arm Vibration is recommended. Measurement
periods of 3 to 15 minutes are often used for Hand Arm vibration. These
increased durations will undoubtedly increase the accuracy and repeatability of
your measured results.
Hand Arm Vibration Transducer Mounting
The supplied mounting block can be attached to the HARM accelerometer using
the supplied screw and tightened using a Phillips screw driver. The mounting
block can then be mounted to the vibration source using hose clamps or plastic
ties. If plastic ties are used it is recommended that they are tightened using a
tie tensioning tool. Attaching devices such as clamps and the accelerometer to
hand held devices may alter the mass of the vibration source and will inevitably
slightly alter the vibration emitted from the device, it is therefore recommended
to keep the mass of hose clips or clamps to a minimum.
Other mounting possibilities to mount the accelerometer to the vibration source
are tapping a stud into the vibration source and attaching the accelerometer to
the stud. Alternatively the stud may be adhered to the device rather than
tapped with an adhesive that dries rigid. Castle Group Ltd can supply a glue and
stud pack if required, (order code KD1215). See
Accessories
for more options.
