Design, Development and Calibration of Virtual System for Relative Humidity Measurement

In the present paper a frequency mode data acquisition technique, which converts directly relative humidity into a frequency signal, is considered. The system is realized using low cost oscillator, multifunction data acquisition board and capability of virtual instrumentation. In order to automate calibration procedures appropriate software (so called virtual instrument) is developed and described in brief. Using possibility of virtual instrumentation or to be more precise the build in LabVIEW probability, statistics and interpolation functions a method to increase calibration accuracy is suggested and put into practice. Following this approach the polynomial calibration equation for capacitive sensor is extracted and saved in transducer electronic data sheets file. As example of proposed approach a virtual system based on relative humidity capacitive sensor is realized. The main objective of this paper is to demonstrate how with virtual instrumentation can be solved some difficult engineering problems such as relative humidity calibration and measurement