FPGA-Based Real-Time Implementation of Temperature Measurement via Tunable Diode Laser Absorption Spectroscopy

In this paper, a real-time temperature measurement system was implemented using a field programmable gate array (FPGA) via tunable diode laser absorption spectroscopy. The system can be used to measure the average temperature along the laser path. The wavelength modulation spectroscopy (WMS) method was applied to realize temperature measurement. First, a recursive peak detection algorithm was proposed to improve the accuracy of main peak detection of WMS signal and reduce the computational complexity. Second, an FPGA was facilitated to realize: 1) a real-time quadrature demodulator to extract the signals at frequencies of <inline-formula> <tex-math notation="LaTeX">$2f $ </tex-math></inline-formula> and <inline-formula> <tex-math notation="LaTeX">$1f$ </tex-math></inline-formula> and calculate the WMS-<inline-formula> <tex-math notation="LaTeX">$2f/1f $ </tex-math></inline-formula> signals on chip and 2) in-situ accurate main peak detection of the WMS-<inline-formula> <tex-math notation="LaTeX">$2f/1f $ </tex-math></inline-formula> signals and hence target gas temperature measurement. Third, experiments were conducted to verify the real-time performance of the system. Experimental results show that the proposed algorithm and hardware design can implement continuous temperature measurement with a temporal resolution of up to 0.25 ms and the measuring rate can reach 4 kHz.