RKI Instruments Beacon 410 - Manual (Page 14)

10 • Internal Description Beacon 410 Gas Monitor Operator’s Manual
Channel Relays & Fail Relay
The eight channel relays are above the channel alarm terminal strip (see Figure 1 on
page 5 and Figure 3 on page 9). These relays are dedicated to specific channels. Figure 3
illustrates the allocation of the channel relays.
The fail relay is located directly to the left of the channel relays. The fail relay is a common
relay.
Common/Channel Relays
The four common/channel relays are above the common/channel alarm terminal strip (see
Figure 1 on page 5 and Figure 3 on page 9). These relays can be configured as either all
channel relays or all common relays in the Global Menu.
Termination Jumper
A two pin header with a termination jumper installed is located near the top edge of the
main PCB to the right of the display cable connector. It is labelled “RS-485 Line
Terminator” on the PCB silkscreen. The jumper has no function unless the Beacon 410 is
wired into a Modbus installation. See “Chapter 9: RS-485 Modbus Output” on page 54 for
a instructions to use the Beacon 410 in a Modbus system.
Ground Stud
The threaded ground stud is used for making connections to earth ground. It is located in
the lower right corner of the Main PCB and is connected through the main PCB to the G
(ground) terminal on the AC terminal strip. A kep nut on the stud may be removed for
installation of one or more user supplied lugs to make wiring connections to earth ground.
This stud is typically used to connect the shield drain wire of shielded cable to earth
ground at the Beacon 410.
Power Switch
The power switch is between the common/channel relays and the fuses (see Figure 1 on
page 5 and Figure 3 on page 9). The power switch turns the incoming AC power source
on and off at the Beacon 410. When the switch is up, the power is on.
Power Supply
The power supply is mounted to the power supply mounting plate which is located behind
the display PCB. The power supply mounting plate is mounted to the main PCB with four
standoffs. The power supply receives AC power from the external power source and
converts it to a DC voltage that is usable by the Beacon 410 circuitry. A polycarbonate
cover prevents accidental contact with the AC terminals on the power supply.
AC & DC Circuit Protection
Two AC fuses are used in the Beacon 410. The two fuses are located on the right side of
main PCB, between the power switch and the AC in terminal strip (see Figure 1 on page 5
and Figure 3 on page 9). They cut off the incoming AC power in the event of a short circuit
or other electrical fault which causes a high current draw in the Beacon 410. They are
housed in vertical fuse holders and are held in each holder by a quarter turn cover. They
are fast blow fuses rated at 6 A, 250 V.
A polyswitch is used to protect the DC power input. It is located on the right side of the
main PCB above the AC fuses and is labelled on the PCB silkscreen as PS9. In the event
of a short circuit or other electrical fault which causes a high current draw in the Beacon
410, the polyswitch will interrupt the DC power if the unit is powered from DC. When the
fault situation is corrected, the polyswitch resets and the unit will continue to operate. The
polyswitch is not user serviceable.