Crowcon Cirrus Point Infrared Detector (4-20 mA Exd)

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Cirrus Point Infrared Detector (4-20 mA Exd) by Crowcon

Cirrus is a third generation fixed point infrared flammable gas detector. It has a lifetime factory calibration and is covered by a comprehensive five year warranty. A fully automatic, remote functional test capability ensures that the unit is always operational without the need to check detectors locally. The novel optical construction uses a well proven dual beam, dual detector arrangement to give optimal long erm performance.

Cirrus also offers complete connection flexibility with the option of Modbus (RS485) serial link to addressable control systems, providing remote interrogation and data collection facility.

Rugged & reliable

Flammable gas detectors have to be totally reliable. This is why Cirrus has two sources delivering two beams, each at different wavelengths and each monitored by measurement and reference detectors. One beam, not sensitive to hydrocarbons, continuously checks the integrity of the optics and provides an on going zero measurement for the hydrocarbon-detecting beam at a different wavelength.

Thus any drift in the IR source is compensated for. IR beams are measured over a larger area than normal meaning the optics in Cirrus are particularly tolerant to shock and vibration.

The rugged optics are mounted in a high grade stainless steel case giving protection in the harshest environments.

Low maintenance

The highly stable optical performance of Cirrus provides a factory calibration that will last for 5 years. Cirrus never requires zero or span gas calibration. The reliability of Cirrus has been assessed independently using MIL Handbook 217F/2/12/91 to give a MTBF of 8.6 years, including the infrared source.

The optical system will function up to 90% obscuration. The system will automatically indicate when obscuration reaches a preset level so there is no need to clean Cirrus until it tells you to.

Cirrus can be fitted with an automatic drop-in filter, which mimics gas and checks the function of the unit, so Cirrus does not need manual or local functional testing.

Where testing is mandatory, Cirrus has a flow adaptor for use with compressed gas and remote gassing points. Interfaces can also be fitted to aid testing of units mounted in inaccessible areas.

Easy installation & upgrade

The docking station of Cirrus simplifies both installation and system changes. It contains connections for field wiring, power transient suppression and convenient access to the RS485 input to Cirrus.

At installation, the docking station is sited and wired up with the detector head being fitted later during commissioning. Future configuration changes are made by simply connecting a PC to the control room, depending upon the system configuration. Cirrus offers easy field configuration.

Ultimate flexibility

Cirrus offers complete connection flexibility with both 4-20 mA and RS485 outputs.

Addressable detectors can be looped together via the Modbus serial link providing remote control and interrogation capability.

Cirrus also offers a pellistor mimic for updating or extending existing pellistor-based systems. This interface converts the 4-20 mA signal of Cirrus into a pellistor-compatible form, which means existing field cabling and control panels can be retained.

Dimensions 240 x 130 x 175 mm (9.5 x 5.2 x 7 inches)
Function Detection of hydrocarbon gases in the 0-100% LEL range, by infrared absorption
Optical system Dual beam, dual wavelength, dual detector
Optical performance Correct operation with up to 90% obscuration Dirty optics warning over 75% obscuration (configurable) Heated window avoids condensation
Operating voltage 18-32 V dc (nominal 24 V), 4 W maximum
Typical output signals All levels configurable:
0 mA: fault
2 mA: dirty optics
4-20 mA: 0-100% LEL
22 mA: over range
Communications Modbus RS485 serial link
Functional testing - automatic
- flow adaptor for gassing
Response time T90 < 10 seconds (including weatherproof cover)
4-6 seconds instantaneous release of gas at high concentrations
Repeatability 2%
Construction Stainless steel 316 ANC4
Weight: 7kg (15.4 lbs)
Temperature range -40C to 65C (-40F to 149F)
Humidity range 0-99% relative humidity
Non condensing
Approval codes Class 1, Zones 1 & 2
EExd IIC T6 (Tamb < -40C to 65C (-40F to 149F))
EExd IIC T5 (Tamb < -40C to 80C (-40F to 176F))
Standards EN50014, EN50018, UL2279
Ingress protection IP66 (jets of water)
IP67 (submersion)
General immunity Totally immune to sunlight and all catalyst poisons
RF radiation Tested to EN55022 class B and meets EN50081-2
RF immunity Tested to IEC801-3 and meets EN50082-2
Warranty 5 years
Gases detected by Cirrus Methane, other alkanes, alkenes, ketones, alcohols, carbon monoxide, carbon dioxide, aldehydes