A flexible measurement system for absorption spectrometry using LED light sources and a high accuracy two-channel ADC for simultaneous sampling

Real time, high resolution measurements of gas concentrations are a task in many industrial applications like smoke detectors, medical and analytical devices. By usage of LED sources for optical absorption spectroscopy, such systems have a high potential to replace commonly used electrochemical sensors, even in low-cost applications. Depending on the gases, they can provide higher sensitivity, selectivity and dynamical response. Background of this paper is the optical gas concentration measurement by usage of LEDs, which are matching the specific absorption lines of different gases. The paper describes in detail a laboratory device, developed for high precision, multispectral (up to 8 wavelengths), referenced (20-bit, two-channel simultaneous sampling) measurement system with temperature stabilized LED sources. While the described system was developed for laboratory purposes with high precision and flexibility in mind, the key components (ADC/LED-Driver) are very low-cost and the system could also be driven by a simple microcontroller.