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New Delhi, India

Islam T.,Jamia Millia Islamia University | Mittal U.,State Physics Laboratory | Nimal A.T.,State Physics Laboratory | Sharma M.U.,State Physics Laboratory
Proceedings of the International Conference on Sensing Technology, ICST | Year: 2012

Surface Acoustic Wave (SAW) based device is very much suitable for detecting very small quantity of vapours of explosive chemicals. There are three possible kinds of SAW devices which can be used for sensor fabrication such as delay lines, resonator and filter. Choice among them depends on individual preferences and sometimes it is the matter of chance. In this paper, a high frequency 70 MHz SAW device has been developed for the detection of chemical warfare (CW) agents. SAW device is fabricated on ST -quartz substrate as it has negligible temperature coefficient at room temperature. The device is having dual oscillator circuit configuration for compensating the effects of temperature, humidity and pressure. Device is coated with suitable polymer and the applicability of the sensor for Dimethyl methylphosphonate (DMMP) detection has been demonstrated. © 2012 IEEE. Source


Saxena R.S.,State Physics Laboratory | Semwal S.K.,State Physics Laboratory | Rana P.S.,State Physics Laboratory | Bhan R.K.,State Physics Laboratory
International Journal of Electronics | Year: 2013

In 2D resistive sensor arrays, the interconnections are reduced considerably by sharing rows and columns among various sensor elements in such a way that one end of each sensor is connected to a row node and other end connected to a column node. This scheme results in total N + M interconnections for N × M array of sensors. Thus, it simplifies the interconnect complexity but suffers from the crosstalk problem among its elements. We experimentally demonstrate that this problem can be overcome by putting all the row nodes at virtually equal potential using virtual ground of high gain operational amplifiers in negative feedback. Although it requires large number of opamps, it solves the crosstalk problem to a large extent. Additionally, we get the response of all the sensors lying in a column simultaneously, resulting in a faster scanning capability. By performing lock-in-amplifier based measurements on a light dependent resistor at a randomly selected location in a 4 × 4 array of otherwise fixed valued resistors, we have shown that the technique can provide 86 dB crosstalk suppression even with a simple opamp. Finally, we demonstrate the circuit implementation of this technique for a 16 × 16 imaging array of light dependent resistors. © 2013 Taylor & Francis. Source


Saxena R.S.,State Physics Laboratory | Bhan R.K.,State Physics Laboratory | Saini N.K.,State Physics Laboratory | Muralidharan R.,State Physics Laboratory
IEEE Sensors Journal | Year: 2011

Two-dimensional resistive sensor arrays that utilize shared row and column connections to simplify the interconnect complexity suffer from the crosstalk problem among its elements introduced due to the interconnection overloading. In this letter, we present a method of overcoming the problem of crosstalk by putting all of the row nodes at virtually equal potential using virtual ground of high-gain operational amplifiers (opamps) in negative feedback. The circuit, though it requires a large number of opamps, solves the crosstalk problem to a large extent and provides faster scanning. We verified the circuit functionality with PSPICE simulations. We have also derived the expressions of crosstalk rejection and sensitivity to show that, by using high-gain, low-noise opamps, we may get excellent performance. © 2006 IEEE. Source

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