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1.
DESCRIPTION
An important point for the practical feasibility of this synchronization is that
the time delay of the paper drive start should be negligible. The clutch of the
Level Recorder Type 230<5, as schematically outlined in Fig. 1.16, is engaged
when no current passes through it and disengaged when excited. It is a non-
slip device and, since the coupling of the paper drive system to the continu-
ously rotating synchronous motor introduces a negligible variation of kinetic
energy in the system, the start of the paper drive occurs practically instantane-
ously when the current is cut. The command is thus made from the signal
recorded on the test disc, by simply actuating a relay device cutting the clutch
circuit at the end of the start signal. This is performed by the synchro-
starter whose block diagram is sketched in Fig. 1.17.
Type 2305
Type
4409
Filter input
Fig. 1.17. Block diagram of the automatic start/stop arrangement (Synchro-
starter of 4409
+
clutch circuit of the 2305 ).
The scanning speeds of both the disc turn-table and the Level Recorder paper
drive are tied by the mains frequency and no mechanical connection is
needed. This allows the turn-table to be installed freely on an antivibration
support which is an important point for precise measurement.
The starting signal is applied to the "Filter Input" terminal of the 4409, and
should have the following characteristics for operating the starter:
Frequency:
Voltage:
Duration:
1ooo Hz
.±
100 Hz.
from o.1 to 32 V r.m.s.
(at
1 kHz).
at least o.1 second.
Note: By means of a relay connected in parallel with the clutch of the Level
Recorder, the syncho-starter is only connected to "Filter Input" when the
connection to the recorder is made and when the paper drive is stopped.
15
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