Improvement in Sensitivity by Circuit Simulation for Humidity Sensor

Abstract

The emerging human comfort life attracts the monitoring of humidity in atmosphere. Particularly, a tiny change in humidity in prosthetic devices alters biological harmony of the living society. However, the tiny change in humidity is very difficult to measure by conventional sensors or hygrometers. Therefore, it is essential to investigate on improvement of sensitivity of a sensor. In resistive type humidity sensors, two electrodes are placed in an interdigitized pattern to enhance the contact area, in which resistivity changes with moisture absorptions in between the electrodes. The present study aimed to further amplify the electric signal to enhance the sensitivity of the sensor by tuning the amplifier-circuit. An operational amplifier (op-amp) is used for the simulation in Proteus software. From the different used op amp, it has been found that without a feedback loop, the op amp works as a comparator. After studying on different feedback loops, we have found that the negative feedback loop used in the present circuit cancels out the noise and varies linearly. Different cases had also taken for all the components in the present circuit to obtain an optimal value, which was maximum by first keeping the input voltage as constant. We considered a certain component value and then changed the input to a very low value keeping the optimum value obtained from the components. Here, we obtained a significant improvement in output for a small change in input signal. Hence, this huge enhancement in amplification () and large sensitivity achieved using the present simulated circuit can be used for humidity sensors.