Modbus® Holding Registers
CET Digital
Gas Detectors
www.critical-environment.com
CGAS-D Digital Gas Detectors
The CGAS-D, CGAS-DP, LPT-M and LPT-P transmitters and the cGas-SC Self Contained Controller may be configured as part of a Modbus® RTU RS-485 network. In order for communication to be successful between devices, be sure your network connection is complete, the network termination switches are set appropriately and all the devices are configured with the same baud rate, character format, etc. Each device will have its own unique Modbus® ID.
NOTES:
- CGAS-D and CGAS-DP can have up to 2 gas channels (or 1 gas and 1 particulate channel) plus an RH channel and a Temperature channel
- The cGas-SC can have up to 3 gas channel plus a horn, strobe, buzzer, RH and Temperature channel
- The LPT-P does not support a relay.
- LPT-P and LPT-M can have up to 3 gas channels.
If you have specific requirements, have any questions or require clarification about these holding registers, please contact CET for assistance.
Holding Registers From 1 to 50,320
| Register | Description | Information | |
| 1 | Internal Relay 1 output status (excluding LPT-P) | ||
| 2 | Internal Relay 2 output status (cGas-SC only) | ||
| 3 | Strobe (cGas-SC only) | ||
| 4 | Internal or External Buzzer (cGas-SC only) | ||
| 30,001 | Channel 1 Reading | present reading x scaler | LEL, PPM, %VOL, μg/m3 |
| 30,004 30,005 | Channel 1 Alarm Status Channel 2 Reading | present reading x scaler | LEL, PPM, %VOL, μg/m3 |
| 30,008 | Channel 2 Alarm Status | ||
| 30,009 | Channel 3 Reading | present reading x scaler | LEL, PPM, %VOL, DegC, DegF, %RH |
| 30,012 | Channel 3 Alarm Status | ||
| 30,013 | Channel 4 Reading | present reading x scaler | LEL, PPM, %VOL, DegC, DegF, %RH |
| 30,016 | Channel 4 Alarm Status | ||
| 30,017 | Channel 5 Reading | present reading x scaler | LEL, PPM, %VOL, μg/m3 |
| 30,020 | Channel 5 Alarm Status | ||
| 40,101 | Number of Relays present (excluding LPT-P) | ||
| 40,103 | Number of Channels present | ||
| 41,013 to 41,028 | Model Name | 32 bytes | |
| 41,035 to 41,042 | Serial Number | 16 bytes | |
| 41,045 | Firmware Version | if changed by program, may require Reset | |
| 41,113 | Modbus ID | if changed by program, may require Reset | |
| 41,114 | Modbus Baud Rate | if changed by program, may require Reset | |
| 45,002 | Relay On Delay (excluding LPT-P) | seconds | |
| 45,003 | Relay Off Delay (excluding LPT-P) | seconds | |
CHANGING ANY VALUES IN THE CHANNEL HOLDING REGISTERS WILL VOID ANY CALIBRATION OR LIABILITY FOR CORRECT OPERATION. THESE VALUES ARE FOR REFERENCE ONLY.
| Register | Description Sensor Scaler | Information |
| 50,004 | Decimal Place | multiplier (1, 10, 100, 1000) |
| 50,005 | Sensor Range | decimals (0, 1, 2) |
| 50,008 | Low Alarm Set Point | with scaler factor |
| 50,011 | Mid Alarm Set Point | with scaler factor |
| 50,012 | High Alarm Set Point | with scaler factor |
| 50,013 | Gas/Value Name | with scaler factor |
| 50,025 to 50,027 | Gas/Value Units | |
| 50,028 to 50,030 | eg. LEL, PPM, %VOL, DegC, DegF, %RH | |
| 50,033 | Priority Membership | |
| 50,079 | Channel 1 Warmup Timer |
Repeat 50,004 to 50,079 for each channel that is present. Each channel has an offset of 80 from the previous channel’s equivalent register.
© 2024 All rights reserved. Data subject to change without notice.
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© 2024 All rights reserved. Data subject
to change without notice.
Documents / Resources
 | CET CGAS-D Digital Gas Detectors [pdf] Instruction Manual CGAS-D Digital Gas Detectors, CGAS-D, Digital Gas Detectors, Gas Detectors, Detectors |