C
12-17 Combustible Gas Transmitter
18
O&M Manual
Rev-D
ALARM ADJUSTMENT
Units supplied with the optional display contain a single alarm setpoint and relay which may be used for
local alarm functions. The SPDT internal relay is ideal for simple applications where only a local lamp or horn is
needed when elevated gas levels are detected.
The alarm setpoint is adjusted using the calibrated dial on the front of the transmitter. The dial is marked 0-
100 corresponding to 0-100% LEL. Note that the alarm setpoint cannot be set for a value below 5%. Simply adjust
the dial to the desired value and the relay will actuate when the combustible gas level reaches that point. When the
relay is activated, a decimal point to the left of the concentration display will indicate that the relay is latched.
The relay is a latching relay and must be reset manually. Reset is done using a magnet through the window
of the display. A magnetic screwdriver is supplied with the transmitter for this purpose. If the relay activates and
the gas concentration returns to normal, simply hold the magnet on the end of the screwdriver against the yellow dot
in the window. The relay will immediately return to a deenergized state. Note that the relay will not reset until the
gas concentration is below the setpoint.
TROUBLE FUNCTION
If the internal relay is not to be used for gas concentration alarming, its function can be changed to a trouble
relay to provide local indication of a fault condition. If the setpoint is adjusted to “0”, the relay will automatically
become a trouble relay. If any of the fault conditions described on page 13 occur, the relay will activate. The relay
is non-latching and will reset if the fault condition clears.
When transmitter trouble is detected, the LCD display will indicate a “-1” value and the current loop will
go to 2 mA. Transmitter operation will return to normal when the trouble condition is corrected.
