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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