Retsch AS 450 control - Handbuch (Seite 29)

Retsch test sieves
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The AS450 is a projection sieve shaker which allows you to enter both the
amplitude and the sieve bottom acceleration as sieving parameters.
In contrast to appliances that are energised at mains frequency and will always
oscillate at the mains frequency of 50 or 60 Hz, projection sieve shakers such as
the AS450 are usually based on a spring mass system excited by a frequency of
40Hz independently of the mains frequency and accordingly different frequencies
arise depending on the different number of sieves or different sieve weights in the
loading.
As long as sieve analyses are to be compared with each other or reproduced
within the respective frequency ranges, setting the same amplitudes and sieving
times will of course produce comparable results.
As a result of the increasing globalisation of production processes throughout the
world, it is becoming more and more necessary to compare sieve analyses from
both frequency ranges 50HZ/60Hz with each other and of course with the results of
your AS450 operating on 40Hz. Due to the different sieving frequencies at
correspondingly short sieving times, it is in no way possible to assume that the
results will be comparable even if these sieving analyses are conducted with the
same amplitude and the same sieving time.
These differences are due to the fact that the important parameter in the shaker
sieving analyses is not actually the amplitude but the sieve bottom acceleration,
which in addition to the amplitude is mainly determined by the frequency. As long
as the sieving analysis is conducted at just the same frequency, e.g. at the same
mains frequency, variation in amplitude is the only way to vary the sieve bottom
acceleration!
To allow for these physical conditions, your new AS450 permits you to set not only
the amplitude but also the display and regulation of the sieve bottom acceleration.
The sieve bottom acceleration is displayed as a multiple of the gravitational
acceleration
“g” (1g = 9.81 m/s²). The functional principle is based on our German
patent no.19 522 987.
For more detailed operating instructions, see the chapter on “Operation of the
AS450” and the paragraph on “sieve bottom acceleration”.
In order to be able to compare sieving analyses in the acceleration mode with
direct input, it is necessary to know the sieve bottom acceleration of the
comparison machine (e.g. an AS200 or another AS450).
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6 Retsch test sieves
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6.1 The highest precision for exact results
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The accuracy and reliability of the analysis result are decided not only by the ability
of a shaker to deliver reproducible results but by the quality of the test sieve
.
Retsch test sieves are high-quality measuring instruments for which only meshes
and perforated sieves that comply with the respective standard are used
6.1.1 Test Sieves with 400-mm and 450-mm Diameters
• standards-compliant production of sieve pans, frame and labelling
• tested 5 times with quality certification
• in conformance to DIN ISO, ASTM, BS
• on request with an individual test certificate for inspection equipment
monitoring in compliance with ISO 9000ff
• Sieve pans made of stainless wire sieve mesh, 20µm to 125mm