Emerson Rosemount 936, Reference Manual

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Table 3-2: Source LED indications
Source status LED color LED mode
Fault Yellow 4 Hz - flashing
Normal Green 1 Hz - flashing
3.3 Output signals
The Rosemount 936 system provides the following outputs:
• 0-20 mA current output
• RS-485 interface
3.3.1 0-20 mA current output
The 0-20 mA output provides the detector status measurements showing a continuous
reading of exact gas concentration.
The 0-20 mA functions as current sink, but it can be reconfigured as source (see Wiring
configurations ).
The maximum permitted load resistance for the 0-20 mA output is 500 Ω.
Table 3-3: Standard 0-20 mA Current for the Gas Channel
Current reading Status and description
0 mA + 0.2 mA Fault in 0-20 mA loop
1 mA ± 0.2 mA Zero calibration (in progress), fault 2
2 mA ± 0.2 mA Fault 1 (non-critical)
3 mA ± 0.2 mA Maintenance call
4 mA ± 0.2 mA No gas present
4 mA - 20 mA Continuous measuring of gas concentration at a range between 0 and
500 ppm.m or full scale
21 mA Concentration is over the range limit (more than full-scale
concentration).
3.3.2 RS-485 interface
The RS-485 input/output sends complete data information to a personal computer (PC)
and receives data or control commands from the PC.
The protocol is Modbus
®
-compatible. The communication with the PC that is operated
through the interface is executed only when used with appropriate host software.
Reference Manual Operating modes
00809-0100-4036 October 2021
Rosemount 936 21