BRUEL & KJAER 2305 - Writing System Mechanism

START-STOP on the Recorder controls the current in the electromagnet.
When current flows in the coil of the magnetic clutch, the motor is discon-
nected from the gear-box, while with no current flowing the motor is mechan-
ically switched in. This method of operating the clutch has been chosen to
avoid the complexity of a rotating electromagnet and slip-ring arrangement.
Lifting Magnet. As the motor can be reversed, it is easy to record a number
of curves on the same sheet of recording paper without losing the syn-
chronization between the Recorder and any externally connected instrument ,
such as an Oscillator or Analyzer. However, to avoid the recording of a
possible
curve when the motor is reversed, an electromagnetic pen-lifting
arrangement automatically lifts the two pens, the writing stylus and event-
marker from the paper when the motor is switched to "Reverse". The
Lifting Magnet can also be controlled externally via the 7-poled REMOTE
CONTROL
jack (see Fig. 1.9), the voltage supply for the magnet then being
taken from the Recorder via the same jack.
Event-Marker. In many cases it may be convenient to mark a certain event
on the recording paper during operation. For this purpose a separate marker
pen has been provided, which marks the outer rim of the paper between
the edge and the perforated holes that slot into the paper drive sprocket.
The movement of the marker pen is operated by means of an electromagnet.
The marking is controlled from the EVENT-MARKNG pushbutton on the
Recorder top panel, but can also be remotely controlled via the REMOTE
CONTROL
jack, Fig. 1.9.
Writing System.
Magnet System. The electrodynamic writing system constitutes a most im·
portant part of the Level Recorder. It has been designed as a closed magnetic
circuit producing a homogeneous field, within which the driving and the
feedback coils move, vide Fig. 1.10. A max. force of approximately 1 kg is
developed
during operation. The coils are guided within the magnetic system
by means of two metal rods and electrically connected via four brushes and
slip-ring strips .
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Fig. 1.10. The electrodynamic writing sy.tem .
fore_ld l ...
' .... pot.rot_t.t
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