A QCM Sensor Array-Based Electronic Tongue With the Optimized Oscillator Circuit Using FPGA

In this paper, an electronic tongue (ET) based on a quartz-crystal microbalance (QCM) sensor array was designed and the methods for sensor data analysis were described. In this regard, as chemical sensors, QCM crystals coated with three different phthalocyanines were employed to discriminate toxic chemicals in liquid media. For sensors' preparation, an automatic coating instrument was developed based on the airbrush technique. The oscillator circuits used in the coating instrument and measurement setup were optimized to minimize the noise and mutual interference of the other oscillator circuits in the sensor array. The designed measurement system, which was responsible for collecting and storing data, communicating with a computer, consisted of a field-programmable gate-array-based control unit. The measurement system collected training data from the sensor array, and then computer application using MATLAB used an artificial neural network to find the composition of toxic chemicals in the sample water. The measurement system was tested for three different toxic chemicals, and the average success rate in predicting them was 4.08%. The desired chemicals can be detectable by preparing the necessary sensor array with the proposed ET.