Low noise, open-source QEPAS system with instrumentation amplifier

Abstract

Quartz enhanced photoacoustic spectroscopy (QEPAS) is a rapidly developing, ultrasensitive method for trace gas sensing. Adequate electronic amplifier, well matched to the quartz characteristics is crucial for overall system performance. Here we present an open source circuit for QEPAS signal amplification. It consists of a buffer, instrumentation amplifier and digitally controlled gain stage. An experiment showed, that it offers signal to noise ratio of about 23 dB better than commonly used transimpedance amplifier. The use of this circuit provides opportunity to improve QEPAS sensitivity by about one order of magnitude.

Quartz-enhanced photoacoustic NH3 sensor exploiting a large-prong-spacing quartz tuning fork and an optical fiber amplifier for biomedical applications

“…Quartz-enhanced photoacoustic spectroscopy (QEPAS), an improved version of traditional PAS, employs a small-size, high-Q-factor quartz tuning fork (QTF) instead of a conventional microphone as a resonant acoustic transducer. The key innovation of QEPAS is the use of the QTF with high resonance frequency (up to several kHz) and narrow frequency band (few Hz or less), which results in an improved immunity of the QEPAS system to ambient noise [18] , [19] , [20] , [21] , [22] , [23] , [24] , [25] , [26] , [27] , [28] , [29] , [30] , [31] , [32] , [33] , [34] , [35] , [36] , [37] , [38] , [39] , [40] , [41] , [42] , [43] , [44] , [45] , [46] , [47] , [48] , [49] . Moreover, QEPAS has a simple spectrophone design and is capable to analyze trace-gas samples of few mm 3 in volume, providing a high detection sensitivity level and fast response time, and hence is very suitable for detecting exhaled gas in real time, as demonstrated in [35] , [36] .…”

High-sensitivity miniature dual-resonance photoacoustic sensor based on silicon cantilever beam for trace gas sensing

“…In recent years, the quartz tuning fork (QTF) featuring high Q-value and small size, has been widely used in PAS [22] , [23] , [24] , [25] , [26] , [27] , [28] . Quartz enhanced photoacoustic spectroscopy (QEPAS) [3] , [10] , [12] , [29] , [30] , [31] , [32] , [33] , [34] , [35] , quartz enhanced photothermal spectroscopy (QEPTS) [36] , [37] , [38] , [39] and light-induced thermoelastic spectroscopy (LITES) [40] , [41] , [42] are typical applications of QTF for high-sensitivity gas sensing. However, the metal conductive electrodes on the QTFs can be easily damaged when measuring corrosive gases, which limits the application of QTF in corrosive gas measurements.…”

Trace CH4 Gas Detection Based on an Integrated Spherical Photoacoustic Cell

“…In 2013, Ma et al used a mid-infrared quantum cascade laser (QCL) as the excitation source to achieve a minimum detection limit (MDL) of 340 parts per trillion (ppt) and 4 parts per billion (ppb) for carbon monoxide (CO) and nitrous oxide (N 2 O) gases under the optimal data acquisition time of 500 s [11]. In order to further improve the amplitude of PA signal, a high-sensitivity quartz tuning fork (QTF) and a fiber-optic acoustic sensor were used to replace the traditional microphone as the acoustic detector [12][13][14][15][16][17][18][19][20][21][22][23]. In 2002, Kosterev et al firstly proposed quartz enhanced photoacoustic spectroscopy (QEPAS) technology.…”