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OP-MR – Open-Path sensors

Atmospheric chemical gases monitoring spectrometer

The OP-MR high resolution atmospheric transmission spectrum provides a finely resolved definition of the chemical species absorption fingerprint and thus a precise measurement of the chemical species concentration. The wide spectral range coverage of FTIR (1.5—13.5 µm) allows the measurement of a large range of chemical species simultaneously. The instrument can provide a full atmospheric transmission spectrum within a fraction of a second


  • The ABB open path spectrometer is configured from the MR Series product line
  • Field rugged setup as a mobile system
  • High linear response of photovoltaic MCT detector
  • For improved chemometric model prediction and precise gas concentration measurements
  • Real time display of gases concentration
  • Open path length up to 500 m
  • Limit of CO2 detection < 10 ppb

The following figure shows and example of gases absorbance IR signature measurement:

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OP-MR 100 m atmospheric transmittance measurement, with study of methane 50 ppm-m emission.

Overview and Characteristics


The instrument is configured for monostatic monitoring; which consist in generating an infrared signal from the interferometer, send this signal to the retro-reflector to be reflected back to the FTIR and collected by a MCT detector. The air path between the instrument and reflector is absorbing part of the infrared signal and provides the atmospheric transmission signature.

OP-MR monostatic monitoring configuration

The silicon carbide (SiC) globar emitted light is modulated by the FTIR before being sent to the retroreflector and collected by the MCT detector after travelling back and forth between the FTIR sensor and retroreflector, thus the only AC signal detected is the IR source modulated energy and all the environment non-modulated energy is DC signal filtered out by the amplifier. Excluding the environment radiance from the air transmittance is important to avoid the addition of environment emitted energy over the air transmission measurement, which would reflect in gas concentration measurement error.

The OP-MR photo-voltaic MCT detector combined with the design of its amplifier provide a highly linear response function in respect to the variation of energy intensity; the linearity of response is very important to precisely model the chemical signature and measure gas concentration.

  • Consists in sending an active signal back and forth to a retroreflector, measuring the transmitted signal through the observation path length
  • The air path between the FTIR and retroreflector is absorbing part of the infrared signal and provides the atmospheric transmission signature
  • The OP-MR monostatic monitoring configuration offers the advantage of excluding the passive radiation emitted by the environment from the measurements


From Spec Sheet:

  • Spectral Range: 740 to 6660 cm−1 (1.5 – 13.5 µm)
  • Spectral Resolution: 1, 2, 4, 8, 16, and 32 cm−1 at all wavelengths
  • Spectral Stability: Better than 0.01 cm−1
  • Scan Speed: 5 cm/s, fixed
  • Sensitivity: SNR 1000 to 1 peak-to-peak
  • Instrument Field of View: 5 mrad (10” Cassegrain telescope)
  • Detectors: 77 K cooled photovoltaic MCT detector (Liquid Nitrogen or Optional: Stirling cooler)


The instrument is delivered in wheel base shipping cases and includes a tripod for the FTIR and the retroreflector case act as its stand. The supplied rugged lap top PC interact with the OP-MR FTIR via a single thin wire Ethernet cable and is pre-loaded with its operating software. The OP-MR setup can be done in a breeze by mounting the FTIR on the tripod, the retroreflector on its case and connecting the Ethernet cable and the power source (AC or 24 volts DC). The viewing ocular (or optional CCD camera) looks through the FTIR telescope, which makes the aiming alignment a simple task.

FTSW100 Software Suite

The FTSW100 modular software provided with the OP-MR instrument is a complete solution for easily applying ABB FTIR technology in process monitoring applications. FTSW100 was developed from the ground up with the rigorous expectations of the process environment in mind. Atmospheric gases monitoring applications are very similar to the process gas monitoring requirement, which makes FTSW100 well suited for atmospheric gas monitoring.

Consult Brochure for more information about the FTSW100 software.



Atmospheric sensing with ABB’s FTIR technology

FTIR technology is well established and widely used for atmospheric chemical characterization, monitoring and sounding applications. The high precision and reliability of ABB’s FTIR instruments has been used for atmospheric analysis over the past 40 years. ABB has provided multiple FTIR analyzers currently operated from the ground, air and space and routinely providing atmospheric transmittance or radiation measurements.

The OP-MR is built from the mature and rugged filed operated MR series of spectroradiometer and the FTSW100 software currently used 7/24 in multiple sites for process control monitoring.

The OP-MR system is well suited to real-time monitoring of air transmission spectrum. It provides absolute air transmittance recording needed to exclude the air transmission factor during IR characterization of various sources of energy to the identification and real-time concentration monitoring of chemical agents.

It is currently used by industrial, military and atmospheric research centers for applications such as:

  • Atmospheric composition analysis
  • Air pollution monitoring
  • Fence-line monitoring at chemical factories
  • Waste land diffuse greenhouse gases (GHG) monitoring
  • Infrared characterization of multiple IR emitted sources.
  • Stand-off detection of chemical clouds
  • Real-time concentration monitoring of chemical agents
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