Crowcon Nimbus Infrared Flammable Gas Detector

  • Discontinued, direct replacement available
  • Approvals ATEX & UL
  • Weight 2.5 kg (5.5 lbs)

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The Crowcon Nimbus is obsolete and replaced by the IRmax.

Using infrared absorption, the Nimbus was a gas detector for hydrocarbon gases.

Rugged & reliable

Nimbus has been designed to be lightweight but rugged. Even in the dirtiest conditions, Nimbus still functions. The optics operate at up to 90% obscuration. While still detecting gas at 75% obscuration, a dirty optics warning flashes so you know when to clean Nimbus. Dust and water ingress are not a problem either, as Nimbus is rated IP66 and IP67. Allied to this Nimbus has full approvals from both EUROPE and North America. Nimbus has an MTBF of 10 years. This figure has been independently assessed using the MIL Handbook 217F/2/12/91.

One person calibration

Nimbus is compatible with Windows software, which means that a Windows-compatible portable PC can be used to check gas levels, find faults and change configurations in the field. Only one person is required to do this. Nimbus is fitted with an optical Communications Interface Module to allow connection of a PC without opening the detector. The configuration and status can be checked remotely using the Modbus serial link for detectors installed in a hazardous area.

Simple maintenance

Nimbus has a local external status light, which shows, at a glance, if the unit is in normal function or fault. When a hazard is detected, it indicates both rising gas and alarm levels. The status light indicates 22 further conditions for instant diagnosis. Nimbus is simple to use even in inaccessible areas. A duct mounting plate is available, incorporating a remote gassing port to allow calibration checking without requiring entry into the duct.

Flexible installation

Nimbus can be integrated into existing situations with ease. It has an RS485 output and dual redundant 4-20mA outputs compatible with metric and imperial armoured cable and conduit. The Modbus serial link allows addressable detectors to be looped, providing a remote control and interrogation facility. For facilities where Nimbus is replacing a pellistor-based detector, the pellistor mimic means that existing cabling can be retained to reduce upgrade costs.

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Title Size
Nimbus Datasheet 892 KB
Nimbus Manual 1 MB
Notice of Obsolescence Nimbus Gas Detector 79 KB

Additional information

Weight 0.09 kg


Model Nimbus
Function The detection of hydrocarbon gases C 1 to C 6 + ethanol, ethylene and LPG in the LEL range by means of infrared absorption. Contact Crowcon for a full list of available gases and ranges.
Dimensions 125 x 170 x 210 mm (5 x 6.8 x 8.3 ins)
Weight 2.5 kg, (5.5 lbs)
Construction LM25 marine grade alloy, polyester powder coated
Optical system Dual wavelength, dual detector
Optical performance Correct operation with up to 90% obscuration
Dirty optics warning above 75% (configurable)
Heated optics to avoid condensation.
Power consumption Operating voltage: 10 to 32 V dc (nominal 24 V)
– LK2 fitted (Anti Condensation Heater) Operating current: 300 mA max (7.2 W @ 24 V, 3 W @ 10 V)
– LK2 not fitted Operating current: 180 mA max (4.3 W @ 24 V, 1.8 W @ 10 V)
Typical output signals All levels configurable – simultaneous sink and source output
0 mA: fault
2 mA: dirty optics
4-20 mA: 0-100% LEL
24 mA: over range
Status light Green – normal function
Orange – fault
Red – detecting gas
22 other conditions indicated by flash rate
Communications Modbus RS485 serial link
Functional testing Flow adaptor for gassing
Accuracy ±2% of gas reading @ ≤ 50% LEL
±5% of gas reading @ > 50% to 100% LEL
Response time <7 seconds – T90
  <3 seconds – instantaneous high levels of gas
Temperature range -40ºC to 65ºC (-40ºF to 149ºF)
Humidity range 0 to 99% RH non-condensing
European Approvals and Standards ATEX II 2G EEx d IIB+Hydrogen T6
  Safety Cert. No: DEMKO01ATEX130838Suitable for use in Zone 1 or Zone 2
Hazardous AreasTamb = -40°C to 65°C EN50014, EN50018
UL Approval and Standards Class 1, Div 1, Groups B, C & D
  Tamb = -20°C to 65°C
UL 1203 (When connected to a class 2 Power Supply)
Ingress protection IP66 (jets of water)
IP67 (temporary submersion), NEMA 4X
Light immunity Totally immune to all external light, both constant and modulated (including sunlight, white light, flashing beacons etc.)
General immunity Totally immune to all catalyst poisons
Electromagnetic compatibility Gas detection standard EN50270
RF emissions EN50081-2
RF immunity EN50082-2

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