Aero-Laser AL 5002 Fast Co-Monitor 1ppb-100ppm Sensitivity VUV-fluorimetry

Aero-Laser AL5002 Fast Co-Monitor 1ppb-100ppm Sensitivity VUV-fluorimetry

Used see photos. Model is still supported by the manufacturer.

From the manufacturer:

"The AL5002 from Aero-Laser is a fast carbon monoxide (CO) monitor with a unique sensitivity below 1ppb (parts per billion).

The detection of CO is based on a VUV-fluorimetry, employing the excitation of CO at 150nm.

This method combines high sensitivity with high selectivity and is linear from 1ppb to 100 ppm. The excitation light is generated by a CW-CO2 resonance lamp, which needs only low maintenance. A monochromator unit, using dielectric mirrors, filters out the VUV from the lamp’s spectrum.

The fluorescence light in the wavelength range between 160 nm and 190 nm is detected by a VUV sensitive photomultiplier followed by a fast counter.

The AL5002 calibrates within minutes, using only a small amount of calibration gas and an in-built zero gas source.

The calibration procedure is fully automatic and can be scheduled in custom-set time intervals.

The gas concentration is displayed in real-time and is logged via a standard RS-232 interface.

Parameter/diagnostic information (e.g. of pressures, flows, temperatures) are logged simultaneously with the measurement data allowing fast troubleshooting of problems.

The instrument consists of a resonance CO2-lamp excited by an RF discharge, an optical filter for selection of the appropriate wavelength interval around 150 nm, and a fluorescence chamber. The emission of the lamp is collimated within the optical filter to a parallel beam of 150 nm light, using off-axis parabola and dielectric mirrors. The VUV-light is then focused on the fluorimeter chamber, where the fluorescence from CO is viewed at right angles by a VUV-sensitive photomultiplier (PMT) with Suprasil pre-optics. The dielectric mirrors in the parallel part of the light beam, provide the spectral band path (bandwidth of ~10 nm full width at half maximum (FWHM) at approximately 150 nm). The optical filter is continuously flushed with dry N2 (purity of 6.0 and filtered to compress organic substances) which is necessary to avoid absorption of radiation in the Schumann-Runge continuum of molecular oxygen and from impurities, in particular, CO. This only requires a flow of ca. 35 ml/min N2 since the volume is very small. The optical filter housing is made from Al covered with a black coating for the reduction of stray light. The air is vented into the fluorimeter chamber, which is connected to an external vacuum pump at the end of the light trap and at the PMT flange, in order to provide well-defined airflow. A pressure sensor and an electrically driven dosing valve stabilize the pressure and the airflow through the cell.

The basic principle is described in detail by Gerbig et al. [1].

[1] C. Gerbig, S. Schmitgen, D. Kley, A. Volz-Thomas, K. Dewey, D. Haaks, An improved fast-response vacuum-UV resonance fluorescence CO instrument, J. Geophys. Res. 104 D1 (1999) 1699"