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8 START-UP
Warning. When the apparatus is connected to its
supply, terminals may be live, and the opening of covers
or removal of parts (except those to which access may be
gained by hand) is likely to expose live parts.
8.1 Instrument Start-Up
In normal operation the instrument displays the Operating
Page which is a general use page in which parameters are
viewed only and cannot be altered. Any changes to the
operating parameters are implemented using the switches as
described in 7.2 Switch Familiarisation. To alter or program a
parameter refer to Section 10. A 5-digit Security Code is used
to prevent unauthorised access to programmable parameters.
The value is preset at 00000 to allow access during
commissioning but should be altered to a unique value, known
only to authorized operators, as described in the Setup
Outputs Page.
When all the required wiring connections and electrical checks
have been correctly made, the power supplies to the various
units may be switched on as follows:
1) Switch on the supply voltage to the 4234 Power Supply Unit.
2) Switch on the supply voltage to the 6553 Monitor unit.
8.2 Alarm Set Point
8.2.1 Type of Alarm Action
The alarm relay coil is energized during normal non-alarm
relay states and is de-energized upon recognition of an alarm
condition, thereby providing 'fail-safe' alarms. i.e. with Alarm 1
set point = 95.0, when the display is indicating greater than
95.0 (plus hysteresis), then Alarm Relay 1 is energized and
Alarm 1 LED is OFF. When the display indicates less than 95.0
(minus hysteresis), then Alarm Relay 1 is de-energized and
Alarm 1 LED is ON. This operating mode ensures that, in the
event of a mains power failure, an alarm condition is signalled.
20
8.2.2
Hydrogen alarm Set Point
It is suggested that the hydrogen alarm set-points should be
based on a reducing percentage of hydrogen as it is displaced
by air entering the application plant. This can be achieved by
setting Alarm 1 and Alarm 2 (if fitted) to give ample warning of
the development of a potentially explosive mixture. Factory
settings are Alarm 1 = 95.0 and Alarm 2 = 90.0 (if fitted).
The procedure is as follows:
Access the programming pages (Section 10) and input the
alarm set-points in accordance with the information given
in Set Up Outputs Page. The hydrogen alarm set point can
only be set with the selector switch in position 1.
8.3 Electrical Calibration
The instrument is factory calibrated for electrical voltage signal
input. No adjustment is normally necessary for proper
functioning of the purge gas monitor. If electrical calibration is
required, a voltage source capable of supplying 10.00mV and
250.00mV is needed. The katharometer input to the monitor
unit should be disconnected and the voltage source signal
applied according to the instructions in the Electrical Cal
programming page (see Section 10).
Note. The 4600 Series instruments incorporate a
two point calibration sequence requiring both zero and
span inputs for a calibration. It is not possible to adjust
either the range zero or the range span scale points
independently.
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