Environics uses proven and tested multisensor technology for chemical detection. This orthogonal method consists of:
- Miniaturized IMS sensor
- Semiconductor/MOS sensors
Data from these sensors is rapidly integrated which leads to real-time reporting of hazard information. The ion mobility cell, patented by Environics, is a modified aspiration type IMS. The IMS spectral fingerprints are measured with multiple electric fields and selectivity is based on the mass, cross-sectional area and charge of the ion i.e. ion mobility. Airflow through the cell is continuous. The semiconductor/MOS cell surface absorbs sample gas molecules which changes its electrical resistance. The resulting resistance changes are reflected in the output of the sensor. Information from each sensor is integrated within the processing algorithm that uses the decision-making capabilities of fuzzy logic. This intelligent processing system leads to a very accurate detection performance and significantly enhances interferent rejection. Operational principle of Environics miniaturized aspiration IMS sensor:
- The sample gas is ionized. This is done with Ni-63 ionization source with activity under exemption limit (<100 MBq) or with Am-241 source, which is similar than in smoke detectors.
- The original ions react with the analyte and form ion clusters which are transported with flowing gas to the measurement area.
- The measurement area is narrow flat channel with electrodes on both sides of the channel. These electrodes are used to create electric field which is perpendicular to the flow.
The ions are transported via the channel with the flow and towards the electrodes by the forces caused by the electric field and charge of ions. The movement depends on the characteristics of the ion: high mobility ions go fast and drop to the first electrodes while low mobility ions travel long time with the flow and hits to the latter electrodes. When the ion hits the electrode, the ion loses its charge. The charges hitting the electrodes are measured as current and the current is used as indication of the existence of certain type of ions.