Design a liquid sensor system based on QCM sensor array by using embedded systems

Nowadays clean water resources are rapidly being reduced around the world. Unfortunately, most pollution is caused by human activities, and a major part of them consists of developing industries. Waste water which contains chemicals washed down drains and discharged from factories is a huge source of water pollution. The world generates billions of tons industrial waste, much of which is pumped untreated into rivers, oceans, and other waterways each year. These facts show that monitoring and controlling pollution in water sources become important day by day. For this reason, in this thesis, a sensor system design which aims to detect the desired chemicals by employing in liquid media has been realized. In this study, an electronic tongue based on 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 (FPGA) based control unit. The measurement system collected training data from the sensor array, and then a computer application using MATLAB used an ANN 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 electronic tongue.