Detcon IR-642 - Manual (Page 19)

to the RS-485 ID number would require the sensor housing to be opened, thus declassif ication of the area would
be required. See section 3.5.4-f for details on changing the RS-485 ID number.
The following section explains the details of the Modbus™ protocol that the IR-622 MicroSafe™ sensor supports.
Code 03 - Read Holding Registers, is the only code supported by the transmitter. Each transmitter contains 6 hold-
ing registers which ref lect its current status.
Register # High Byte Low Byte
40000 Gas type Sensor Life
Gas type is one of the following:
01=CO, 02=H2S, 03=SO2, 04=H2, 05=HCN, 06=CL2, 07=NO2, 08=NO, 09=HCL, 10=NH3, 11=LEL, 12=O2
Sensor life is an estimated remaining use of the sensor head, between 0% and 100%
Example: 85=85% sensor life
Register # High Byte Low Byte
40001 Detectable Range
i.e. 100 for 0-100 ppm, 50 for 0-50% LEL, etc.
Register # High Byte Low Byte
40002 Current Gas Reading
The current gas reading as a whole number. If the reading is displayed as 23.5 on the display, this register would
contain the number 235.
Register # High Byte Low Byte
40003 Alarm 1 Setpoint
This is the trip point for the f irst alarm.
Register # High Byte Low Byte
40004 Alarm 2 Setpoint
This is the trip point for the second alarm.
Register # High Byte Low Byte
40005 Status Bits Status Bits
High Byte
Bit 7 Not used, always 0
Bit 6 Not used, always 0
Bit 5 Not used, always 0
Bit 4 Not used, always 0
Bit 3 1-Unit is in calibration 0-Normal operation
Bit 2 1-Alarm 2 is ascending 0-Alarm 2 is descending
Bit 1 1-Alarm 2 is normally energized 0-Alarm 2 is normally de-energized
Bit 0 1-Alarm 2 is latching 0-Alarm 2 is non-latching
Low Byte
Bit 7 1-Alarm 2 Relay is energized 0-Alarm 2 Relay is not energized
Detcon Model IR-640/IR-642 Carbon Dioxide Sensor PG.19