Design and Analysis of a parametric insensitive Direct Digitization scheme for Four-Wire Resistive Sensor

Design and analysis of a direct-digitization scheme for four-wire connected resistive sensors is detailed in this work. The basic principle involves computing the time-interval taken to store charge in a capacitor and the time taken to discharge it. The time interval is shown to be proportional to the value of unknown sensor resistance. The output of the scheme is a digital representation of the sensor analog value and is insensitive to circuit parameters like resistance of connecting wires, analog switch impedance or controller port resistance. The resistive sensor is directly connected to the controller through analog switches and hence has lesser number of components. Simulation of the proposed scheme indicates an overall error within 0.0022%. Emulation indicates an overall error within 0.031%. The paper also details the error analysis of the proposed scheme.