Tieliang Lv

Tunable diode laser absorption spectroscopy (TDLAS) has been widely applied in industrial gas detection, but traditional calibration methods face challenges including high standard gas consumption, exorbitant costs, and heavy calibration workloads—particularly under wide temperature and pressure ranges, where variations in laser parameters can introduce significant errors. This study proposes a simplified calibration method for peak-locking TDLAS systems based on wavelength modulation spectroscopy (WMS). First, a coupling relationship model between the modulation index (m) and amplitude modulation (AM) is established, and an iterative calibration method is developed to synchronously adjust the laser operating current and temperature, enabling both m = 2.2 and AM = 0.1 to converge to their target values simultaneously, thereby eliminating the need for per-device temperature–pressure–concentration ternary calibration. Subsequently, the effects of quadratic nonlinearity in the laser power–current (P-I) and wavenumber–current (v-I) curves on detection accuracy are systematically analyzed for both 2f/1f and 4f/1f WMS representation methods. The simulation results obtained within a temperature range of 300 K ± 100 K and a pressure range of 1 atm ± 0.2 atm show that, for 2f/1f-WMS, a v-I nonlinearity rate of ±5% yields a maximum detection error of no more than 0.11% (with the error peak occurring in the 40–65% concentration range and no zero offset), while a P-I nonlinearity rate of ±5% results in a maximum error of no more than 0.82%, nearly independent of concentration. By comparison, the 4f/1f-WMS scheme effectively suppresses the zero offset induced by P-I nonlinearity, achieves lower detection errors, and requires only span calibration for each device. The proposed method significantly reduces the calibration workload and cost of TDLAS systems while ensuring detection accuracy.

The application of oxygen sensors based on Tunable Diode Laser Absorption Spectroscopy (TDLAS) in the industrial field has received extensive attention. However, most of the existing studies construct detection systems using discrete devices, making it difficult to apply them in the industrial field. In this work, through the optimization of the sensor circuit, the size of the core components of the sensor is reduced to 7.8 × 7.8 × 11.8 cm³, integrating the laser, photodetector, and system control circuit. A novel integrated optical path design is proposed for the optical mechanical structure, which enhances the structural integration and long-term optical path stability while reducing the system assembly complexity. The interlocking design of the laser-driven digital-to-analog converter (DAC) and photocurrent acquisition analog-to-digital converter (ADC) reduces the requirements of the harmonic signal extraction for the system hardware. By adopting a high-precision ADC and a high-resolution pulse-width modulation (PWM), the peak-to-peak value of the laser temperature control noise is reduced to 2 m°C, thereby reducing the detection noise of the sensor. This oxygen detection system has a minimum response time of 0.1 s. Under the condition of a 0.5 m detection optical path, the Allan variance shows that when the integration time is 5.6 s, the detection limit reaches 53.4 ppm, which is ahead of the detection accuracy of similar equipment under the very small system size.

Hydro-generators in pumped storage power stations (PSPSs) consist of multiple rotor windings connected by lead wires, which are consistently subjected to large stress due to the frequent starting and stopping, making fatigue fractures of these lead wires common. This paper proposes a fault early warning system featuring a dual-connection lead wire and a real-time fracture monitoring system to ensure high reliability of the lead wire. A fatigue testing machine is developed and the reliability of real-time fracture monitoring mechanism is proved through the validity test on this machine. Subsequently, through analysis based on the P-S-N model, the relationship between the fatigue life of the lead wire and the displacement amplitude of the external force it withstands was studied. This relationship can be used to predict the redundant time of dual-connection lead wires, providing reference for maintenance personnel to schedule shutdowns for generators. Conversely, this relationship can also guide lead wire designers to quantitatively adjust the expected redundant time by adjusting the lead wire’s structure, to meet the needs of practical applications.