Crowcon Nimbus gas controller

Register map(s) for this device, each at the trust rung it earned. Addresses are 0-based as on the wire; word order and scaling are only confirmed at the hardware-verified rung.

interop-verified

Read + decoded cleanly over a real network vs an independent third-party Modbus test server (transport and framing; reads are remapped into the server's register window, so the map's own addresses are NOT exercised). Does NOT prove word order/scaling against the actual device.

point	address (0-based)	type	scale	unit
gas_level	99	I16	0.1	% FSD
mode	100	I16	1	enum
status	101	I16	1	enum
detector_signal_rate_of_change	102	I16	0.01
inst_gas_reading	103	I16	0.1
obscuration_factor	104	I16	0.1	%
supply_voltage	105	I16	0.01	V
temperature	106	I16	0.1	oC
gas_det_level_at_zero	303	I16	1	raw
ref_det_level_at_zero	304	I16	1
temp_at_zero	305	I16	0.1	oC
gas_det_zero_drift	306	I16	1
ref_det_zero_drift	307	I16	1
temp_at_auto_zero	308	I16	0.1
gas_det_signal_gain_at_fsd	309	I16	1
ref_det_signal_gain_at_fsd	310	I16	1
temp_at_fsd	311	I16	0.1
level_2_alarm_threshold	499	I16	0.1	% FSD
level_1_alarm_threshold	500	I16	0.1	% FSD
level_1_falling_alarm_threshold	501	I16	0.1
level_2_falling_alarm_threshold	502	I16	0.1
alarm_threshold_hysteresis	503	I16	0.1
lamp_sense	575	I16	0.1
supply_voltage_test	576	I16	0.01
reg_supply_sense	577	I16	0.001
temperature_test	578	I16	0.1

link settings as documented (unverified): RTU; default 9600 8N2; unit ID 1; FC 03,16; RS485 half-duplex multi-drop asynchronous serial communications link.

bench facts as documented (unverified)

A/B polarity	differential of between 2 and 6 volts
isolation	conforming to the RS458 standard (-7 to +12 volts)
wiring notes	2 wire, half duplex, multi-drop
max registers/read	125
response timeout	500 ms
inter-frame delay	10 ms
broadcast	supported
protocol notes	Global address 000 is used for broadcast requests, which are validated and actioned but not responded to.
model register	0
serial register	4
firmware register	1
FC 43 device ID	not supported
power	supply set to 24 volts
doc revision	Issue No: 3, Date: 09-Mar-06

generated by gemini:gemini-3.5-flash · harvested from https://site.jjstech.com/pdf/Crowcon-Pdf/Fixed-Gas-Detectors/Nimbus/Nimbus_Modbus-Map_Manual.pdf (Crowcon); manual-faithful — the document's claims, panel risk: ELEVATED — panel is not confident; proved interop-verified on 2026-06-10 · recorded 2026-06-10

The trust ladder

Each rung states what it proved and what it did not. Gray until proven; green is earned by hardware only.

generated — A prompt produced it. Unproven — anyone can regenerate this.
structure-verified — Decode path is structurally sound (addresses, widths, finite values). Does NOT prove word order or scaling.
interop-verified — Read + decoded cleanly over a real network vs an independent third-party Modbus test server (transport and framing; reads are remapped into the server's register window, so the map's own addresses are NOT exercised). Does NOT prove word order/scaling against the actual device.
simulator-verified — Decoded correctly against a protocol emulator seeded with known-true values — catches word-order/scaling errors vs the emulator, not the physical device.
hardware-verified x1 — Matched a real device with operator-attested readings as ground truth — the only rung that confirms word order + scaling on the wire.

Have a device that isn't here? Upload its register map — generation is free, and the connector earns its rung by being proven, not claimed.

Need it proven on your own device? Hardware verification — if it doesn't verify, you don't pay.

Building a platform? License the verified library — machine-readable maps, firmware matrix, API access.