Although there are variations the principal optical design of traditional infrared (IR) point detectors comprises incandescent broadband light sources, optical filters, a beamsplitter, and solid-state photodetectors.
The presented design is different, applying state-of-the-art MEMS (Micro Electro Mechanical System) technology for the optical filtering and the light source (emitter).
In this design, a proprietary Silicon MEMS chip disperses, focuses, and modulates the light transmitted through the detector’s measuring cell. More precisely, the chip switches at a frequency of 1 kHz between two optical states focusing either light where hydrocarbons do absorb or light at reference wavelengths onto the photodetector. The gas concentration is then calculated from the ratio of the light intensities reaching the photodetector in both states.
The micro-fabricated light emitting layer on a MEMS emitter is typically less than 10 µm thick. Compared to a “traditional” miniature filament incandescent lamp, a MEMS emitter of equivalent emitting area will have a greatly reduced mass. Thus it requires much less input energy in order to reach its operating temperature and will have significantly reduced sensitivity to shock and vibration.
MEMS enables a very robust, simple optical design with a minimum number of components: One light source, mirror and window, MEMS chip, and one photodetector. Aging of light sources or solid-state photodetectors will therefore not affect the gas concentration calculation, simply because the same components are used for the gas and the reference measurement.
MEMS technology is also ideal for gas detection with extremely low power consumption. The technology was utilized to develop a battery-powered gas detector that communicates wireless. This detector is designed for harsh industrial environments with no zero and no span drift in a wide operating temperature range.
Christian Heinlein joined GasSecure – now part of Dräger – in 2013. In his position as product manager he contributed to developing the collateral, product training and technical support concepts for the first wireless gas detector for industrial applications.
From earlier positions, amongst other with NEO Monitors, he has extensive knowledge in the field of infrared gas detection using tunable diode laser and MEMS technology.
Christian Heinlein holds a master degree in electrical engineering from the Technical University Braunschweig and a PhD in electronics from the Norwegian University of Science and Technology.