Emerson MRLDS-450 Installation And Operation Manual page 26

IMPORTANT: To prevent intermittent alarm operation at the setpoint due to measurement
noise, this instrument implements hysteresis at the setpoint. Once the alarm level is
exceeded, the gas measurement must return a fixed percentage below the alarm threshold
before the alarm is disabled. Typical hysteresis value is set at 5% of full scale; however,
this is sensor-specific and non-editable.
Alarm Latching
Enabling alarm latching will maintain alarm or fault condition even after the alarm
or fault condition is no longer active. When latched, the alarm or fault condition
must be manually acknowledged before the condition will be cleared. This allows
transient alarm or fault conditions to be identified.
If an alarm is latched, for example, the condition has occurred but is no longer active,
an acknowledgment button will appear on the Home screen. Select this button to
acknowledge the latched condition and clear the alarm or fault.
When disabled, the alarm or fault status clears automatically as soon as the condition
is no longer active. To configure:
• On the Configure tab select Alarm then Alarm Latching. Select Enable/Disable
and OK to confirm.
4.2.3.6. Modbus Configuration
Address
Sets instrument address for connection to RS-485 Modbus interface. (Default: 1). 
To set address:
• On the Configure tab select Modus, then Address. Select 1-247 and OK to confirm.
IMPORTANT: Ensure all instruments on RS-485 bus have been configured with unique
node addresses. If two instruments have been configured with same address, bus contention
will occur preventing communications with these instruments via the RS-485 interface.
Baud Rate
Sets instrument baud rate for connection to RS-485 Modbus interface (Default: 9600
baud). To set baud rate:
• On the Configure tab select Modus then Baud Rate. Select 9600/19200 and OK to
confirm.
22 • MRLDS-450 Refrigerant Gas Detection I&O Manual
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026-1316 Rev 0