Spectrex SafEye Quasar 902 Open-Path Gas Detector
Industrial IR/DOAS open-path hydrocarbon gas detection for pipelines, processing equipment and exposed hazardous facilities. The Quasar 900 family monitors a wide area using separated optical source and receiver.
Original manufacturer: Spectrex / Emerson, distributed by Prosense in Türkiye.
| Model | Quasar 902 |
|---|---|
| Optical path range | 15–40 m |
| Measurement | Open-path combustible hydrocarbons |
| Technology | Infrared Differential Optical Absorption Spectroscopy (DOAS) |
Emerson publishes FM and IECEx approvals for the Quasar 900 system. Certification of the detector, source, accessories and installation must be confirmed for the precise part numbers. Do not extrapolate the Quasar 900 approval to other Spectrex families.
Original Manufacturer Documentation
Emerson original Quasar 900 model page →
Prosense distribution reference and Quasar 901–904 model ranges →
Spectrex Quasar 902 — precise beam class and system wiring
The original Emerson SafEye Quasar 900 datasheet uses 15–40 m for this transmitter-and-receiver combination. It can be appropriate for intermediate perimeter lines and process unit escape routes, subject to actual coverage design. The delivered equipment and approved gas calibration must be independently identified.
| Parameter | Original Emerson specifications | Engineering interpretation |
|---|---|---|
| Paired optical hardware | Receiver QR-X-11X plus source QT-X-21X (maker part-family format) | The receiver and xenon source are two separate aligned devices, not a standalone point detector. |
| Qualified beam length | 15–40 m optical installation distance | Model 901–904 differences are primarily calibrated transmitter path-length classes; a path outside this range requires reconsideration. |
| Measurement variable | 0–5 LEL·m for methane/propane; 0–8 LEL·m for ethylene | LEL·m is integrated combustible-gas loading along the beam, not %LEL or ppm concentration at a particular point. |
| Minimum reported concentration-length | 0.15 LEL·m manufacturer stated detection limit | A small cloud concentrated in part of the path can equal a larger diluted cloud; coverage modeling is essential. |
| Response and alignment | <2 s OEM electronic response; ±0.5° optical misalignment tolerance | Time to detect a spatially separated plume still depends on cloud intersection and alignment. |
| Supply / typical draw | 18–32 V DC, 24 V nominal; receiver ~220 mA, emitter ~240 mA | Provide powered field cabling to both optical devices and include heated-optics reserve. |
| Output-state coding | Gas 4–20 mA; normal 4 mA; 3 mA maintenance; 2 mA blocked beam; 1 mA calibration; 0 mA fault | A beam blocked at 2 mA must never be treated as a valid zero-gas reading. |
| Additional communication | RS485 Modbus and HART for diagnostics/configuration | Check the correctly ordered interface and commissioning software, not generic Modbus on every control system. |
| Environmental proof | −55 to +65 °C, 95%RH noncondensing, heated optical face and stainless 316 housing | Optical heaters reduce condensation but do not remove the need for field checks. |
| Certificate boundary | Original manufacturer lists FM, ATEX, IECEx and SIL2-related approvals for specified systems | Match receiver, source, cable entries and exact approval marking before hazardous-zone use. |
Coverage, diagnostics and installation
Although 902 overlaps 901 from 15–20 m and 903 from 35–40 m, the actual source/transmitter pairing must be ordered for this range. The optical path only measures gas when the gas cloud crosses the field between aligned devices; supplementary point detection can be needed near leak sources. Arrange source/receiver brackets and line-of-sight access so maintenance can test blocked-beam, misalignment, dirty optics, and real gas simulation independently. Verify HART/RS485 addresses and prove the 0/1/2/3 mA conditions in the control system before connecting any emergency shutdown action.
Source documentation: Emerson official Quasar 900 OEM product · Original Emerson Quasar 900 technical data sheet (00913-0100-4035 Rev AE, July 2023, hosted by supplier). Reconcile certificates and ordering code against the current OEM manual before installation.
AirAlign technical editorial review · 25 October 2026. Meter-long gas response is an open-path safety-system design issue, not point ppm concentration or automatically full-site SIL2 approval.