Development of Electronic Hygrometer System

Abstract

Hygrometers are generally applied in the meteorological (weather) stations, industries, laboratories and at homes to determine the moisture content in the air or humidity. They could be of mechanical or electronic design. This paper presents a cheap, affordable and efficient electronic means of measuring and controlling humidity at homes and in industries. The system comprises of: a power supply unit, a humidity sensor/buffer unit, a precision half-wave rectifier/amplifier unit, an ac source generator, a buffered analogue (Vcc/2) reference ground unit and an output unit (a meter and switching control). It has the ability to measure the relative humidity automatically. Above a preset level of 80%, the switching control output through the action of two Darlington transistors operates a relay which in turn switches on any device connected to it. This device tends to dry up the air surrounding the sensor thereby reducing the relative humidity. And once the value drops below 80%, the device deactivates. The hygrometer can be used to provide a direct display of the relative humidity and control the switching of some appliances such as air conditioners and air dryers, once the value exceeds 80%. The electronic hygrometer thus plays a significant role in humidity measurement and control environments by providing or allowing a high level of accuracy, faster response time and lower levels of hysteresis.