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| Working Group 5.45 |
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Certification of Length Measuring Machines
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Length measuring machines
In many cases, trade and industry make up accounts on the basis of length measurements
or their combinations (area, volume) on commodities of the most different kind. In these cases,
the measuring instruments must have been approved for verification or their conformity must have
been certified in accordance with Directive 2004/22/EC. The testing and research activities of the
Working group are focussed on these conformity assessments or approval procedures in accordance with
the Verification Act for log wood and choirometers.
A focal point are the length measuring machines for textile area-measured materials,
for which it is today even possible to measure the length of extremely flexible materials
with relative uncertainties of less than 0.3%. With the aid of the laser Doppler technology,
the limits of mechanical scanning methods were overcome, and length measurements with low
measurement uncertainty became possible even on tuft-coated textiles. The test of a novel
measuring method based on optical position correlation has already shown that it will be
possible to further reduce the measurement uncertainies. Another instrument group serves for
the measurement of restiform materials (in particular cables). Here it has become possible
to increase the feed rate of the product to be measured to up to 17 m/s, while complying
with the maximum permissible error on verification for the length measurement. In future,
the length measurement on light pipe cables will also be performed automatically, for which
new technologies are to be expected. These will again require the development of new test
procedures and associated regulations.
Length measuring machine for flexible textiles
Volume measuring device for packages
Of great importance are measuring instruments which allow the area or the volume to be determined
by non-contact optical-electronic screening. To these instruments belong the area measuring machines
which are mainly used for irregularly limited leather surfaces. Here, the relative measurement
uncertainty could be reduced to less than 1%, and the feed rate of the product to be measured
could be increased to up to 1 m/s.
Trunk wood measurement by means of ultrasound scanning
In the case of volume meauring instruments, the required dimensions are obtained by scanning -
on the basis of which the volume is calculated. Examples are measuring instruments which serve
to determine the smallest enveloping cuboid of packages for aviation. In timber industry, novel
measuring instruments - the so-called log wood measuring facilities - have lately been used to
an increasing extent. These facilities measure the length and diameters of the logs automatically
and calculate - on the basis of these measurements - the volume to be invoiced in business.
By virtue of EC regulations, carcasses must be classified with choi-rometers which, in Germany,
are subject to mandatory verification. The instruments, which work with opto-electronic systems
or ultrasound, measure the thickness of specific layers of the biological product to be measured
and determine from it the trade classes for the price to be paid for the carcass.
Invasive Choirometer
© Physikalisch-Technische Bundesanstalt
Page created: 26-Sep-2006, last update: 18-Sep-2007 01:32 PM,
K. Eggert |
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