Operational Principle of Water Level Detector for Agricultural and Domestic Use

Abstract

This paper proposes a design to automatically detect the level of water in a reservoir (storage tank) at a preset level and initializes an information to the users in case of low water level. The functionality of this sensor depends basically on the electrical conductivity of water (probes) which varies, depending on the level of its impurity. It is of this note that the electrical conductivity of saline (35g/kg at 25oC) is 4.8S.m^-1, while the electrical conductivity of high quality drinking water ranges between 0.0005 – 0.05 S.m^-1, and that of deionized water is 5.5 x 10-6 S.m^-1. In this sensor system, an actuator that operates on the basic principle of an astable multivibrator, operating with a duty cycle of 50.25% with an output frequency of 3.256Hz is required to operate on the water level detection. Hence, a continuous train of rectangular pulses whose band width is 0.154s at a period of 0.306s was designed and developed for the system. The device is powered by a dual power source for redundancy sake, reliability and maximum efficiency.

Keywords: Astable multivibrator, duty cycle, charging and discharging time, bandwidth and electrical conductivity