Open Path FTIR Spectrometer

Open-Path FTIR Spectrometer

CAC has developed an open path FTIR (OP-FTIR) spectrometer to measure gas emission rates from nearby sources. The OP-FTIR spectrometer measures the gas concentration in the atmosphere over an extended path, typically up to 130 m. While the instrument has been developed by CAC to measure agricultural emissions and fire emissions, the system can be used to measure the concentration of multiple infra-red active gases in the atmosphere including for example boundary emissions from industries and fugitive emissions from pipelines or gas and coal fields.

The heart of the OP-FTIR design is a Bruker infra-red spectrometer and a modified Schmidt-Cassegrain telescope which expands and projects the infra-red beam to a distant retro-reflector. The reflector returns the beam to a mechanically cooled MCT detector at the spectrometer. The instrument is mounted onto a heavy duty tripod via an Automated Instrument Mount (AIM) that allows the instrument’s orientation to be alternated between up to 6 reflectors. The system operates continuously under the control of software written by CAC. The concentration of the target gas is analysed in real-time using the MALT analysis program.

In typical operation of the OP-FTIR system, the measurement path is located downwind from the gas source, for example a fire or livestock, and perpendicular to the predominant wind direction, with the gas carried from the source into the measurement path by the wind.

Contacts: Dr Frances Phillips, Prof David Griffith