Detection of chemical vapors using oscillator with Surface Acoustic Wave

Senzori sa površinskim akustičkim talasima (PAT) ispoljavaju superiornu osetljivost pri detekciji hemijskih agenasa. Zbog nepostojanja pokretnih delova i izrade kompatibilne sa modernim tehnologijama, PAT hemijski senzori su veoma pouzdani. Senzor je modelovan kao dvoportni uređaj čiji su delovi predstavljeni ekvivalentnim kolima. Izračunata je promena izlazne frekvencije u funkciji koncentracije gasa. Projektovano je oscilatorno kolo sa PAT senzorom u grani povratne sprege. PAT senzor se koristi za modifikovanje frekvencije oscilacija. Prisustvo hemijskih isparenja se onda direktno detektuje praćenjem ovog frekvencijskog pomaka.Surface Acoustic Wave (SAW) sensors demonstrate superior sensitivity in detection of chemical agents. Due to their solid state design and fabrication compatible with modern technologies, SAW chemical sensors are extremely reliable. The sensor is modeled as a two-port device with parts represented by equivalent circuits. Change of output frequency as a function of vapor concentration is calculated. The oscillator circuit with SAW sensor in the feedback loop is designed. The SAW sensor is used for modifying the oscillator frequency. The presence of chemical vapor is then detected by monitoring this frequency shift

Detection of chemical vapors using oscillator with Surface Acoustic Wave

Senzori sa površinskim akustičkim talasima (PAT) ispoljavaju superiornu osetljivost pri detekciji hemijskih agenasa. Zbog nepostojanja pokretnih delova i izrade kompatibilne sa modernim tehnologijama, PAT hemijski senzori su veoma pouzdani. Senzor je modelovan kao dvoportni uređaj čiji su delovi predstavljeni ekvivalentnim kolima. Izračunata je promena izlazne frekvencije u funkciji koncentracije gasa. Projektovano je oscilatorno kolo sa PAT senzorom u grani povratne sprege. PAT senzor se koristi za modifikovanje frekvencije oscilacija. Prisustvo hemijskih isparenja se onda direktno detektuje praćenjem ovog frekvencijskog pomaka.Surface Acoustic Wave (SAW) sensors demonstrate superior sensitivity in detection of chemical agents. Due to their solid state design and fabrication compatible with modern technologies, SAW chemical sensors are extremely reliable. The sensor is modeled as a two-port device with parts represented by equivalent circuits. Change of output frequency as a function of vapor concentration is calculated. The oscillator circuit with SAW sensor in the feedback loop is designed. The SAW sensor is used for modifying the oscillator frequency. The presence of chemical vapor is then detected by monitoring this frequency shift

Polyaniline thin films in sensors for detection of toxic welding vapors

In this paper the possibilities of applying sensors based on filters with surface acoustic waves (SAW) for the detection of harmful products in welding processes are analyzed. This review discusses the sensing mechanism and configurations of the sensors. The principles of SAW sensors are considered with special emphasis on the application of conducting polyaniline nanocomposites as sensitive thin layers in sensors for the detection of CO, NO2, and COCl2. The literature suggests the use of In2O3 as a dopant for CO and NO2 detection sensors, and ethylenediamine and phenylenediamine in COCl2 sensors. The paper presents original results of modeling of sensors that are designed for detection of CO and NO2 for which there are experimental data in the literature. The results obtained based on this model are in excellent agreement with results from the literature, which shows the validity of modeling. Based on the developed modeling methods, calculations were done for sensors for the detection of these gases in which the structure was the surface of quartz. From these modeling results it can be concluded that the use of the quartz substrate provides better sensitivity. In addition, the quartz sensors are thermally stable

Modeling and design of surface acoustic wave filters and their military applications

The operation principles of surface acoustic wave filters (SAW) and materials and technology of their fabrication are presented. A special attention is paid to wide and diverse applications of SAW filters in signal processing, communications and chemical sensors, stressing their military applications. An original method, developed by the authors, for the modeling and prediction of SAW filter characteristics is presented. The abilities of the method are illustrated by the examples of chemical SAW sensors for the detection of warfare chemical agents. The designed and fabricated SAW filter PAT-FPO is the base for the special purpose chemical sensors