Choi, Minyoung Cho, Gyuwon Hwang, Seyeon Lee, Jinwoo Kim, Yangmo Kim, Jeongmin Kim, Kyunghoon So, Hongyun Choi, Sun 2025-10-16T11:30:06Z 2025-10-16T11:30:06Z 2025-10-16 2026-02 0925-4005 https://pubs.kist.re.kr/handle/201004/153340 This study demonstrates the capability of wavelength modulation spectroscopy (WMS) based on tunable diode laser absorption spectroscopy (TDLAS) using a hand-held field-programmable gate array (FPGA) system. Programmable FPGA-based TDLAS-WMS hygrometer (PFTWH) enables measurement of water vapour concentrations over a broad range (70？5800？ppm) for applications in climate science. This system incorporates a custom-designed digital lock-in amplifier (DLIA), optimized for water vapour detection. For the DLIA, a 100？Hz cut-off frequency and a finite impulse response filter with a windowed-Hamming design and a 200-tap coefficient were used. The PFTWH demonstrated simultaneous processing capability of 1？f and 2？f signals by programming the DLIA on a commercial FPGA board. To quantitatively evaluate DLIA performance, we introduced an integrated WMS system that enables parallel operation of a commercial FPGA-based TDLAS-WMS hygrometer (CFTWH), the PFTWH, and direct TDLAS (dTDLAS). The 1？f and 2？f signals are extracted from both the CFTWH and PFTWH, while the dTDLAS provides reference concentration information for performance assessment. The linearity and accuracy of the designed PFTWH were validated by comparison with the CFTWH. Additionally, long-term measurements of water vapour concentrations across the broad range (70？5800？ppm) were successfully performed with a time resolution of 0.1？s, maintaining stable performance over 1000？s with 30？s averaging. Furthermore, both PFTWH and CFTWH were demonstrated to meet uncertainty, accuracy, and precision requirements for airborne measurement. English Elsevier BV Programmable FPGA-based TDLAS-WMS hygrometer (PFTWH) for broad-range water vapour detection: Quantitative assessment of digital lock-in amplifier (DLIA) performance via integrated WMS system (I-WMS) Article 10.1016/j.snb.2025.138930 1 Sensors and Actuators, B: Chemical, v.448 Sensors and Actuators, B: Chemical 448 N scie scopus 001600315400006 Chemistry, Analytical Electrochemistry Instruments & Instrumentation Chemistry Electrochemistry Instruments & Instrumentation Article WAVELENGTH MODULATION SPECTROSCOPY DIODE-LASER MU-M ABSORPTION-SPECTRUM SENSOR DESIGN SPECTROMETER CALIBRATION VALIDATION ABSORBENCY Hygrometer DLIA (Digital Lock-In Amplifier) FPGA (Field-Programmable Gate Array) Water vapour sensing TDLAS(Tunable diode laser absorption spectroscopy)