Increasing the sensitivity of the Senseair alcohol analyzers

Purpose and goal:

The pre-study has been devoted to exploring how is possible to increase sensitivity of the alcohol analyzers manufactured by Senseair AB in order to realize operation in “sniffer mode”. These are non-dispersive infrared (NDIR) analyzers operating in the mid-infrared (Mid-IR) range. It was necessary to investigate how it was possible to increase the optical path that affect the sensetivity of the devices and the possibility of replacing mechanical choppers with liquid crystal modulators.

Expected results and effects:

Two problems were explored in the pre-study: 1) clearing up how to improve the reflectance of the aluminum mirrors used for multiple reflections, in order to achieve a long optical path in a miniature device, and 2) how to design and implement a liquid crystal modulator whose frequency is much higher than that mechanical light modulator currently used by Senseair AB.

We also clarified which of the operating modes for liquid crystals must be used for the Mid-IR modulators, which materials can be used and where these modulators can be manufactured Approach and implementation:

The purpose of the preliminary study was to understand the main reasons for optical loss on Senseair´s aluminum mirrors, which are used to increase the optical path of light. The higher the reflection of the mirrors, the higher the optical path and, as a result, the higher the sensitivity of the device. The mirrors were studied with ellipsometric methods to determine the optical constants and topology of the surface.

We investigated the type of transparent material that can be used to increase the reflectivity of the mirrors.