Remote sensing of relative humidity

Relative humidity, temperature measurement and monitoring are very useful for the purpose of analysis. The variation in relative humidity and temperature at a particular place may be caused by factors such as power failure or equipment failure. This paper uses basic knowledge in combining analog circuit and digital circuit theory together with programming techniques to handle control of the hardware. The temperature and relative humidity sensing circuit converts the relative humidity and temperature into analog signals, which are then applied to a micro controller based data logger for storage purposes. The data are then transferred to a computer through a RS232 standard serial port. The user interface program will handle the data transfer between the data logger and the computer as well as allow the user to input important parameters such as sampling interval and starting date and time for the logging operation. A backup power supply is also connected, included to sustain operation in case of power failure. The system can perform both real time and also stand-alone methods.