Highly sensitive and selective CO sensor using a 233 μm diode laser and wavelength modulation spectroscopy

Abstract

A ppm-level CO sensor based on a 2f wavelength modulation spectroscopy (2f-WMS) technique was developed for the application of SF 6 decomposition analysis in an electric power system. A detailed investigation of the optimum target line selection was carried out to avoid spectral interference from high purity SF 6 in a wide wavelength range. A diode laser emitting at 2.33 μm and a 14.5-m multipass gas cell (MGC) was employed to target the R(6) line of the CO first overtone band and increase the optical path, respectively, thus resulting in a minimum detection sensitivity of 1 ppm. A Levenberg-Marquardt nonlinear least-squares fit algorithm makes full use of the information from all data points of the 2f spectrum and as a result, a measurement precision of ~40 ppb was achieved with a data update rate of 0.6 s. The sensor performance was also evaluated in terms of the gas flow rate, stability, and linearity. The results showed that the best operating condition with a precision of 6 ppb can be achieved by increasing the gas flow rate to the value that matches the optimum averaging time of 48 s.

Application of Micro Quartz Tuning Fork in Trace Gas Sensing by Use of Quartz-Enhanced Photoacoustic Spectroscopy

“…A small gas sampling volume is always desired in the measurement such as microorganism respiration [47], human breath [48], and atmospheric air [49]. According to the geometry of the QTF, the calculated gas sampling volume of the micro QTF is ~0.1 mm 3 , which is several orders of magnitude smaller than conventional photoacoustic spectroscopy (PAS) sensor [50,51] and tunable diode laser absorption spectroscopy (TDLAS) sensor [52]. For a typical QEPAS system, the gas flow rate was limited to 200 sccm (standard cubic centimeter per minute) in order to avoid gas flow noise [27].…”

Quartz Enhanced Photoacoustic Detection Based on an Elliptical Laser Beam

“…Trace gas detection techniques play an important role in the fields of environment, industry, aerospace, and medical technology [1][2][3][4][5]. Various optical sensing methods for atmospheric monitoring have been reported by numerous researchers [6][7][8][9][10]. Compared with other optical spectroscopic techniques, photoacoustic spectroscopy (PAS) technology is one of the most effective approaches for trace gas sensing, in which a microphone is employed to detect acoustic signals generated by the modulated optical radiation in a weakly absorbing gas [11][12][13].…”

A Sensitive and Reliable Carbon Monoxide Monitor for Safety-Focused Applications in Coal Mine Using a 2.33-$\mu$ m Laser Diode

“…Such a sensor, employing a 2.3 μm laser diode, has attracted significant attention in recent years and a number of CO sensors have been reported and applied across a diverse group of industries [17]- [20]. Examples include a compact and calibration-free CO sensor with an in-line reference cell [21], a real-time in-situ CO sensor in a pulverized-coal-fired power plant [22], a ppm-level CO sensor for application to early fire detection [23] and a sensitive CO sensor used for SF6 decomposition analysis in an electrical power system [24]. Among these methods, the technique of 2f wavelength modulation spectroscopy (WMS) was adopted in the reported CO sensors.…”