Simple Technique for Measuring Air Humidity Using an IBM Microcomputer

Abstract

A thermocouple consisting of copper and constantant wires has been used as a relative humidity detector and was interfaced to an IBM microcomputer. The temperature differences between the wet and dry junction of the thermocouple were used to calibrate the relative humidity of air. The generated e.m.f. signal was amplified and thus converted to a digital signal using an analogue-to-digital converter (ADC). The digital data output of the ADC was then passed to an IBM microcomputer via a programmable peripheral interface (PPI) chip to process, display and store the relative humidity data. The relative humidity profile in the range 23–32°C of the dry bulb temperatures for a specific day can also be plotted and analysed. The measured relative humidity was compared to a commercial humidity meter and showed good agreement.