10
Medical Gas Central Alarm - Medipoint 125 Digital Alarm
4233500107.03
1.6.2 Power supply printed circuit board
The power supply PCB is retained inside the alarm panel
back box with four retaining studs and connects to the
processor PCB multi-way ribbon cable by polarised
connectors. The power supply PCB incorporates four
mains terminals (2 Earth, Neutral and Live, see figure
8) connected to a matching plug/socket combination
to accept the mains electrical power supply, which
preferably should be from an essential circuit, and
enables connection of flying earth leads which electrically
bond the assembly.
A filter protects the alarm system from possible spikes
or disturbances of the incoming electrical power supply
and an integral transformer provides 24 V d.c. Supplies
to operate the alarm circuits and power the pressure
sensors. A 5x20mm fuses to BS EN 60127 protect the
power supply circuits. F1 is rated at 500mA for 230V
supplies and (see figure 8).
In order to prevent inadvertent cross connection, the
mains electrical power supply plug and socket is not
mechanically compatible with any other connection to
the PCB.
A miniature ’Maintenance Mute’ push button (see
figure 8) is fitted on the power supply PCB and is
accessible with the alarm panel front cover open. With
an alarm condition displayed, operation of this button
’permanently’ disables audible reinstatement for that
particular displayed alarm condition only. This facility
is designed for use when the plant or pipeline is shut-
off for a prolonged period. On returning the pipeline
pressure to NORMAL this feature automatically re-sets
without further manual selection.
Each channel (designated 1 to 5) incorporates five
terminals (figure 8) which are for connecting to the
medical gas source equipment.
A relay (complete with optional line contact monitoring
circuit) suitable for switching 50V and a maximum of 0.5
Amps is fitted to the power supply PCB (see figure 8).
The relay has volt free, normally open contacts and two
terminals (N/O and C) enable connection by a matching
plug/socket combination to either a Medipoint central
alarm system or other suitable system. The line contact
monitoring circuit can be from the on screen setup
menus. The relay is de-energised and contacts open
when any of the twelve alarm conditions are initiated.
Terminals are also provided to enable connection of a
remote audible warning device (AUD+ and AUD-) (see
figure 8).
It is recommended that the input cables from the source
equipment and data transmission are installed separate
from the mains cable.
Figure 8 - Power supply PCB.
Mains
Fuse [F1]
Mains
Filter
24V DC
Power supply
Remote Audible
Connection [+] [-]
Output Relay For Transmitting Single Event Alarm
[COMMON] [N/O]
Gas Service Connections, Channel 1-5
Data Transmission connections
IN [A] [B], out [A] [B] and [Screen]
Main Power Connection
[BONDING EARTH]
[MAINS EARTH]
[NEUTRAL] [LIVE]
Maintenance
Mute
Multi way ribbon cable
connector to processor PCB
Backup
Battery Pack
End of Line
Resistors
Switches
