Crosstalk suppression in networked resistive sensor arrays using virtual ground technique

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 NxM 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 4x4 array of otherwise fixed valued resistors, we have shown that the technique can provide 86dB crosstalk suppression even with a simple opamp. Finally, we demonstrate the circuit implementation of this technique for a 16x16 imaging array of light dependent resistors.