Retsch AS 300 - Manual (Page 16)

07/02/2012 Retsch GmbH
16
Information on sieve plate acceleration mode
The AS300 control is a throw sieve which allows you to set
both the amplitude and the sieve plate acceleration as
sieving parameters.
Throw sieves such as the AS300 control are generally based
on a spring/mass system which is exited in inherent frequency.
This means that in contrast to machines exited at mains power
frequency which always oscillate at 50 or 60 Hz, varying sieve
frequencies set in here when loaded with different numbers of
sieves and sieve weights. However, the spring/mass system
has been designed in such a way that the inherent frequency
range is always kept somewhere near 50 and 60 Hz.
As long as sieve analyses are only to be compared with each
other or reproduced within the respective inherent frequency
ranges, setting the same amplitudes and sieving times will
naturally produce comparable results.
However, the increasing globalisation of production processes
nowadays often requires sieve analyses made in both mains
power frequency ranges 50/60Hz to be compared with each
other, and naturally also with the results of your AS300 con-
trol exited at inherent frequency. Even if these sieve analyses
are conducted with the same amplitude and sieving time, the
disparate sieve frequencies are likely to adversely affect the
comparability of results at reasonably short sieving times.
The reason for these differences lies in the fact that the essen-
tial parameter in throw sieve analyses is not amplitude, but
rather the sieve plate acceleration, which is crucially influ-
enced by frequency as well as amplitude. Provided that siev-
ing is only carried out at the same frequency, e.g. with the
same mains power frequency, varying the amplitude is natu-
rally the only means of varying the sieve plate acceleration!
In order to take account of these physical facts, your new
AS300 control enables not only the amplitude to be set, dis-
played and regulated, but also the sieve plate acceleration.
The sieve plate acceleration is shown as a multiple of the
Earth's gravity "g" ( 1g = 9.81 m/s
2 ). The functional principle
is based on our German patent No. 19 522 987.
See the chapter on "Operating the AS300 control" and the
paragraph "Sieve plate acceleration" for more details on op-
eration.
Comparative sieve analyses in acceleration mode with direct in-
feed nevertheless require that the sieve plate acceleration of
the comparative machine (e.g. a AS200 control or another
AS300 control) is known.
If the sieve plate acceleration is unknown, our EasySieve R
evaluation software enables you to input comparative data both
much more simply and in a greater scope, thus, for example,
there is also the option of time correction.