Agriculture Reference
In-Depth Information
and 65% relative humidity of air. The slides are
scanned by a Minolta Dimage Scan MultiPro at
4800 dpi (Langenhagen, Germany). Scanner
software Dimage Scan 1.0 in combination with
Photoshop 5.0 LE (Adobe Systems GmbH,
Munich, Germany) is used to process the data.
An adapted set-up has been developed to
measure the width of the prepared fibres and
fibre bundles.
from the length class lines painted on the
ground plate. Based on the amount of fibres in
each length class (Fig. 10.4.), the distribution
can be calculated.
LENGTH MEASUREMENT USING AN ALMETER
.
The
Almeter (Siegfried Peyer AG, Switzerland) is
an electronic apparatus for measuring length
and has been developed to test wool fibres
(Fig. 10.5). The device works with a speci-
men of fibres aligned in parallel using a
preparatory machine called a 'Fibroliner'.
Detailed information has been published by
Grignet (1981), where he stresses the impor-
tance of sample preparation by the Fibroliner.
The Fibroliner has to be modified for bast
fibre bundles like hemp. The number of nee-
dles per comb must be changed from 153 for
wool to 75 for bast.
The Fibroliner prepares a sample by rear-
ranging the fibres or bundles, with all having
one of their ends situated approximately on a
line perpendicular to the direction of the
fibres.
As shown in Fig. 10.5, the Almeter itself
consists of two parts assembled in the same
housing: a device for measuring the local
sum of the cross-sectional areas of the speci-
men and an electronic unit that calculates
the length distribution automatically during
measurement.
The device for measuring the local sum of
the cross-sectional areas consists of a specially
designed rectangular condenser with dimensions
Length
As shown in Table 10.3, two methods were
chosen to test the fibre and fibre bundle
length.
1. A manual method, which allows a cheap
and easy way to characterize the length
distribution of a sample.
2. An automatic system, for a quick deter-
mination of the length distribution of fibres and
fibre bundles up to a length of 260 mm.
LENGTH MEASUREMENT USING TWEEZERS
.
In this
single-element testing method, the length of
the whole element is measured in straightened
state. The crimped fibre or fibre bundle has to
be straightened with an adequate force, avoid-
ing elongation. The instrumental set-up of the
measurement is displayed in Fig. 10.3. The
edge on the left side is the starting point for
measurement, where the fibre end is fixed by
the weight. The fibre is then drawn by using
the tweezers with low force, to avoid elonga-
tion. The length of the fibre can now be read
Weight
Piece of velvet
Length class
Guide pin
Edge
(start point)
Fibre
Fig. 10.3.
Length measurement using tweezers.
