CI Systems Atmospheric Transmission Measurement System

CI-Systems have developed the Atmospheric Transmission Measurement system to measure absolute spectral transmission values with an accuracy of few percent.

Spectral measurements are taken in the range of 0.4 – 14.0 μm at distance of up to 6km, and the system can measure in highly absorbing atmospheres (fog, haze, low visibility, etc.,). It is designed to be field useable with simple deployment and the ability to operate 24/7. 

The Atmospheric Transmission Measurement System is based on a telescope-collimated and optically chopped source located at the far end of the transmission path, with a measurement instrument (SR-5000N spectroradiometer) at the near end. The spectroradiometer is locked onto a chopped signal produced by the source and a method known as synchronous detection (or lock-in amplification) is employed to recover the measurement signal. The source is typically chopped at frequencies of 500Hz and the detector (spectroradiometer) is locked to the source in both frequency and phase. Any detected signal that is not at the exact frequency and in phase with the source is cancelled out by the synchronous detection circuitry implemented in the SR-5000N. This detection method ensures that, although the chopped signal may be small relative to the absolute signal entering the collecting aperture of the radiometer, only the source signal is measured and all other radiation is rejected, thereby providing the highest possible SNR for long-path atmospheric transmission measurements.

The chopping frequency reference is transmitted to the spectroradiometer by RF link over long distances,  or by cable over short (<=500m) distances. Details of the SR5000N Spectroradiometer can be found by clicking on the related products section on the left of this page.

Since this is a highly customised system, please contact us to discuss specification details:  E: [email protected]   T: 01582 764334