Photoacoustic Spectroscopy Using a MEMS Microphone with Inter-IC Sound Digital Output

In photoacoustic spectroscopy that is adopted for gas sensing, microphones are usually used to detect the pressure variation inside the sample cell. The application of a new commercial inter-integrated circuit sound digital micro-electro-mechanical systems (MEMS) microphone that is enhanced with a filter and an analog-to-digital converter in a single package is presented. The utilization of the described MEMS microphone together with an embedded microcontroller significantly reduces the required space and costs for the components needed to realize the signal detection path of the spectrometer. The measurement results of this signal detection path are compared with those of a conventional photoacoustic spectrometer that is equipped with a capacitive microphone, a microphone preamplifier, and a lock-in amplifier for signal processing. At the first stage of our study, the recorded 24 bit data streams of both microphones are evaluated. At a second stage, the digital output signals of the MEMS microphone are processed with the Goertzel algorithm. The results are compared with the digital output of a lock-in amplifier that is connected to the microphone preamplifier's output of the condenser microphone.