Stability design of a light-emitting diode light source for trace constituent concentration measurement

摘要

Optical measurement is widely applied in determining the concentration of trace constituents in oilfield injection water. The performance of the light source directly affects the accuracy of the whole optical measurement system. To guarantee the stability of the infrared light source and the ultraviolet (UV) light source, an infrared light-emitting diode (LED) with the central wavelength of 860 nm and a UV LED with the central wavelength of 365 nm were chosen. Both LEDs were modulated to high frequency to shield the stray light. Through the analysis and comparison among the double-load current-source drive mode, single-load voltage-source drive mode, and single-load current-source drive mode, we designed and theoretically deduced a closed-loop control system for the single-load current-source driving LED. The experiment validated that this system could effectively eliminate the light intensity instability caused by the drift of ambient temperature and light emitting efficiency, and ensure the intensity stability of the light source in the determination of trace constituents. (c) 2017 Optical Society of America