Electronic interface for a gas sensor system based on 32MHz QCMs: design and calibration

This paper describes the design and development of a system of gas sensors based on quartz crystal microbalances (QCMs) to be used for the measurement of gas, vapors, and their mixtures. This system's architecture manages an array composed of eight QCMs with a resonance frequency of about 32 MHz. Custom oscillator circuits were designed and built to drive the QCMs. A data acquisition stage was developed to collect the output frequencies of the QCMs array and to visualize and store the data. The QCMs have been functionalized with eight different types of anthocyanins, using two different techniques. Three of the QCMs composing the array have been tested, and their performance is compared to a previous array based on 20-MHz QCMs. One of the QCMs, covered via drop casting, when tested in a calibration experiment, shown an improved performance consisting in a ratio of 4.92 between 32- and 20-MHz sensitivities. This number confirmed the ratio of 5.76 theoretically calculated using Sauerbrey's law. The other two QCMs tested were covered via spray casting, giving resolution of tens of ppb, comparable with the previous release.