Evaluation of a simple PC-based quadrature detection method at very low SNR for luminescence spectroscopy

We developed a PC-based phase measuring system based on the principles of quadrature detection with ideal features for accurately determining the amplitude and phase of a sinusoidal signal, even in the presence of very high noise levels. This detection technique was implemented via software on a personal computer (PC), and its response was analyzed using experimental tests under different noise conditions using 1 s test signals. Additionally, this technique was implemented and was subsequently evaluated using a real measurement system (a versatile and low-cost optical-fiber measurement system for optically detecting oxygen in the gas phase) under different lighting conditions. The results demonstrate the robustness of the proposed technique to noise and its computational efficiency; these results were similar to those obtained using a measuring instrument commonly used in research laboratories (a commercially available digital lock-in amplifier (LIA)).