Multi-channel impedance measurement system for polymer humidity sensors.

• An impedance analyzer for studying the sensitivity of humidity sensors is proposed. • Efficiency is improved by 32-channel measurement technique. • Range and accuracy are improved by automatic switching range and compensation method. The design of a high performance, multi-channel impedance measurement system for humidity sensing characteristics test of polymer humidity sensors is presented. The relay modules with negligible contact resistance are designed to accomplish 32-channel measurement and automatic switching range. The division of the wide impedance range and the selection of the corresponding feedback resistance for automatic switching range are so designed as to satisfy the actual scale range of the ADC module for getting high accuracy measurement. An algorithm of compensation considering the parasitic parameters both in the measurement and feedback circuits is designed to further improve measurement accuracy. The whole measurement is automatically implemented by a field-programmable gate array for signal generation and logic calculation and a digital signal processor for frequency-spectra analysis. The results of the uncertainty analysis and tests revealed that our system was quite adequate to efficient humidity sensing characteristics test as opposed to the existing devices. [ABSTRACT FROM AUTHOR]