Operation; General - Robertshaw 365A Instruction Manual

MODEL 365A & E365A INSTRUCTION MANUAL
VIBRASWITCH® MALFUNCTION DETECTOR 909GF294

4 OPERATION

4.1

GENERAL

The Model 365A & E365AVibraswitch® (Ref. Figure 4-1) is sensitive to vibration in a direction (the
sensitive axis) perpendicular to its mounting base. It contains an acceleration sensitive mechanism, which
also functions as a "mechanical amplifier", to activate a snap action switch when the selected level of
vibration is exceeded and the detecting mechanism "trips".
Figure 4-1. Operating Principal for the Vibraswitch®, Model 365A & E365A
The detecting mechanism consists of an armature suspended on a flexible pivot, which is restrained from
motion by a permanent magnet (the hold down magnet). In the "armed" condition, the armature is held
against the stop pin by the hold down magnet. The stop pin maintains a precise air gap between the
armature and the hold down magnet. On the opposite end of the armature, the compression spring
provides an adjustable force to oppose the force of the hold down magnet. Whenever the peak vibration
inertial force (mass x acceleration) plus the adjustable compression spring force exceeds the force of the
holding magnet, the armature is released and is pulled into the latching magnet (tripped position).
Simultaneously, it activates the snap action switch. This detecting mechanism has a uniform response
from 0 to 300 Hz over a range of 0 to 4.5 g's.
The mechanism may be reset to the "armed" position manually (locally) or electrically (remotely).
Manually, depress the RESET button to move the armature away from the latching magnet ("tripped"
position) until it is held against the stop pin ("armed" position). Electrically, the reset coil may be
activated to pull the armature into the "armed" position against the stop pin.
A reset/holding coil, when specified, is provided, in the DC or AC voltage as specified, so that accidental
shutdowns on starts can be prevented. External time delay relay circuits are required to maintain voltage
at the holding coil during startup period and then release this voltage when operation is normal. At full
voltage, the reset coil should not be energized for more than four (4) minutes to prevent overheating.
Then, the reset coil must be de-energized for a period of 10 minutes before reenergizing. For longer hold-
in requirements, the rest coil should be energized at full voltage and then held-in at one-half the rated
voltage.
The Vibraswitch®, Model 365A &E365A may be used in conjunction with the Vibraswitch® Monitor,
Model 563A. The Monitor is a solid state electronic system designed to "sort out" false signals received
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