ABSTRACT
Devices with an active sensing material and signal transducer are called sensors. The function of the active sensing material and signal transducer in sensors is to transmit the signal without any magnification from a selective compound or from a change in a reaction (Wilson & Gifford, 2005). Sensors produce any one of the signals as electrical, thermal or optical output signals which could be converted into digital signals for additional processing. One of the methods of categorizing sensors is done based on these output signals (Sakaguchi et al., 2007). Among these methods of classification, the electrochemical sensors have more advantages over the other sensors because in electrochemical sensors, electrodes can sense the materials which are present surrounded by the host without doing any damage to the host system. Moreover, sensors can be generally classified into two categories such as chemical sensors and biosensors (Chen & Chzo, 2006).
