GAS Gasmaster, Инструкция по установке, эксплуатации и обслуживанию

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2.9.5. RS-485 communications
Gasmaster can provide alarm and system information
to PLC/DCS/SCADA systems via a two-wire link using
the Modbus RTU protocol (9600 baud, 8 data bits, no
parity, 1 or 2 stop bits). Up to 16 Gasmaster systems
can be ‘multi-dropped’ on a single two-wire link with a
maximum cable length of 1 Km, two-core twisted pair
cable is recommended. Single Gasmaster systems that
are to communicate via the RS-485 link should have the
RS485 TERM link made, which connects a terminating
resistor. For multi-dropped systems the RS485 TERM
link should be removed from all Gasmasters except the
last unit on the line.
A Modbus specification document is available from Gas
Alarm Systems on request.
The RS-485 terminals on Gasmaster systems ordered
with the optional local communications connector will
be used for terminating the connector leads. These
leads must be removed if a remote RS-485 serial link is
required.
2.10 Applying power
Before applying power ensure that any control
or shutdown systems to which the Gasmaster is
connected are inhibited. Once all field cables have
been installed, the batteries can be connected as
per the diagram attached to the chassis plate. (Refer
to section 4.4.) Gasmaster will not power up until an
external power supply is applied.
Apply power to Gasmaster from either the AC or 24 V
dc external supplies. Outputs are inhibited for a preset
time after power-up, and the system will perform a
start up sequence testing alarm indicators and the
internal sounder. If after a settling period faults are
reported, check the sensor connections again or refer
to “Faults menu” on page 24.
When power is applied the green Power LED will
illuminate and flash every 5 seconds to indicate that
the system is operational.
If the external supply fails, Gasmaster will continue to
operate from its internal batteries and the Power LED
will flash every second. Depending on configuration,
Gasmaster will display either a Warning (Warning LED
lights and the sounder will beep every 5 seconds) or a
fault (the Fault LED and sounder will activate, and the
fault relay will change state).
Gasmaster should display all channels being
monitored. Allow sensors to settle before commencing
calibration, refer to sensor instructions supplied with
detectors for recommended settling times.
Note: your Gasmaster is supplied pre-configured, refer
to the Specification and Inspection Certificate provided
with your system. If no channels are configured,
Gasmaster will display the following screen:
To configure your system go to page 25.
2.11 Battery back-up times
Gasmaster is fitted with 1.2 Ah batteries to provide
continued operation in the event of a power loss.
Examples of typical back-up times are provided
below for a system in a non-alarm state, relays set as
de-energised and with the 4-20mA outputs unused
(system current consumption without detectors is
approximately 50mA):
2. Installation