Cell replacement on Combi sensors
Should a sensor cell require to be replaced, the sensor should have its power removed
before changing the cell itself. Flammable (Catalytic) and Toxic cells have colour coded
wiring which is Pink, Yellow and White which should be connected correctly according to
the markings on the PCB. Fig 5 on page 43 and data sheets C893 & C894 at the end of
this document detail the procedure for setting up a new sensor independent of the Combi
panel and then when connected to Combi follow the above zero and span procedure.
Setting the Time to Alarm
Using
ENGINEER’S
menu 26, the time in seconds required to detect a direct 4-20 alarm
can be set to a maximum value of
255
seconds. This is useful in certain installations where
transient gas presence is allowed and gas detection alarms quickly become a nuisance.
The
UP (1)
and
DOWN (5)
buttons change the channel and the
+ (4)
and
– (2)
buttons
will alter the time in increments of 1 second.
Pressing
SELECT (3)
will present the same choice for the addressable channels.
Pressing
SELECT (3)
again returns to the
ENGINEER’S
menu after saving these times.
Setting Alarm levels
The high and low alarm points for the sensors can be set manually using
ENGINEER'S
menu 21 for direct 4-20 alarm levels and menu 15 for addressable alarm levels.
Menu 15 for addressable sensors
Use
UP (1)
and
DOWN (5)
, to choose a sensor which requires an alarm change.
Use
+ (4)
and
– (2)
to adjust the low alarm point.
Pressing
SELECT (3)
will then request you to set the High alarm point.
Pressing
SELECT (3)
again allows the Over Range alarm to be set.
Use the
RESET
button
(7)
to select RISING and FALLING alarm.
Pressing
SELECT (3)
again will exit the menu and save the parameters to memory.
Setting Number of Decimal Places
(18)
Using
ENGINEER’S
menu 18, the number of decimal places displayed by the ‘Gas Value’
can be set to 1 or 2. This is global command for direct sensors only. For addressable
sensors the decimal places selection must be set individually at the sensor via PC
hyper-terminal, (see Combi sensor datasheets C893 & C894).
The
RESET (7)
button changes this menu from the ‘Alter Gas Type’ screen to the
‘Change Range’ screen. On the Change Range screen use
RESET (7)
to switch between
‘DP=1’ and ‘DP=2’. This toggles the displayed Gas Value between 1 and 2 decimal
places respectively.
Press
SELECT (3)
to return to the
ENGINEER’S
menu.
Setting the 4~20mA Deadband
(18)
Using
ENGINEER’S
menu 18, the 4~20mA deadband can be switched ON or OFF.
This is a global command for direct sensors only. For addressable sensors this must be
set individually at the sensor via PC hyper-terminal, (see Combi sensor datasheets C893
& C894). The
RESET (7)
button changes this menu from ‘Alter Gas Type’ screen to the
‘Change Range’ screen.
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