Sensing material interface circuit

As chemo-resistive sensors are based on a change in conductivity at high operating temperatures, so main circuit blocks required for interfacing these sensors are driving circuits for micro-heaters, temperature control units and sensing material interface circuits. 

Sensing material interface circuit, the design of this interfacing circuit is one of the main challenging components of a resistive gas sensor. This is because ... 

Resistance controlled oscillator circuit for gas sensing material interface (adapted from Grassi et a ., 2007). Q and Q are two complementary signals at the output of the flip flop. 

Logarithmic compression circuit for gas-sensing material interface (adapted from Barrettino eta ., 2002). (Voon,roi is a voltage applied from outside which will fix the voltage across the sensing material and thus fix the current at the reference arm of th are two output terminals of the circuit.)... 

In photovoltaic detectors, also called photodiodes, electrons and holes generated by photons are separated by an electric field formed at a potential barrier within the device. This field is formed at a specifically introduced interface in the material, for instance a p-n junction. Photodiodes used in astronomy are almost always made of intrinsic material. When an electron-hole pair is created at the junction by a photon the electron drifts to the -region and the hole to the p-region. The separation of charge causes a voltage to be generated across the detector terminals, which can be sensed directly or, alternatively, a current can be measured when the circuit is completed. 

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