Retsch AS 200 control - natural frequency Manuel d'utilisateur télécharger pdf (Page 22)

Retsch GmbH 22

Information on the sieve bottom

acceleration mode

The AS 200 control is a throwing-type sieving machine which

gives you the possibility of specifying both the amplitude and

the sieve bottom acceleration as sieving parameters.

Throwing-type sieving machines, such as the AS 200 control,

are usually based on a spring-mass system which is excited by

the natural frequency. This means that, in contrast to sieving

machines which are excited only by mains frequency, a sieving

machine excited by the natural frequency is independent of the

voltage supply.

As long as sieve analyses are to be compared or reproduced

within the respective natural frequency ranges specifying the

same amplitudes and sieving times will of course also give

comparable results.

As a result of increasing globalisation of product processes

throughout the world it is becoming more and more important

to compare sieve analyses from sieving machines excited by

mains frequencies in both mains frequency ranges 50/60 Hz

with each other, and also of course with the results of your AS

200 control, excited by natural frequency. Even if these sieve

analyses are carried out at the same amplitude and the same

sieving time, it still cannot be assumed that the results will be

comparable, owing to the different sieving frequencies at

appropriately short sieving times.

The reason for these differences is the fact that with throwing-

type sieve analyses the important parameter is not really the

amplitude but the sieve bottom acceleration. This, together

with the amplitude, is determined mainly by the frequency.

As long as sieving is carried out only at the same frequency,

e.g. at the same mains frequency, variation in the amplitude is

of course also the only possibility of varying the sieve bottom

acceleration.

To take these physical facts into account your new AS 200

control now provides you with the possibility of specifying

display and control of the sieve bottom acceleration in

addition to the amplitude. The sieve bottom acceleration is

indicated as a multiple of the acceleration due to gravity “g” (1

g = 9.81 m/s²). This functional principle is based on our

German patent no. 19 625 808.

For more detailed operation instructions see the section

“Operation of the AS 200 control and the paragraph “Sieve

bottom acceleration”.

However, comparative sieve analyses in the acceleration mode

with direct input presupposes that the sieve bottom

acceleration of the comparison machine is known (e.g. an AS

200 control or another AS 200 control).

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Retsch AS 200 control - natural frequency Manuel d'utilisateur Page 22

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