We have developed novel humidity and gas detector system using quartz crystal oscillators (QCO) deposited with cellulose Langmuir-Blodgett (LB) films. We have realized stable humidity detection by the LB-based QCO sensor for extremely high humidity subsequent to the water dipping condition. Also, specific gaseous molecules such as alcohol could have been sensitively detected.

This paper describes a circuit analysis technique that includes all circuit elements used in transistor Colpitts quartz crystal oscillators. This technique is applied to a quartz crystal oscillator that has a tank circuit for selecting the oscillation frequency. The results obtained with this technique are compared with SPICE simulation results. Good agreement in the results clearly shows the validity of our technique.

This paper describes a simulation technique of start-up characteristics that considers a nonlinearity of the drive level of quartz crystal resonators. A nonlinear resonator model for SPICE where the resonant resistance varies with the voltage added to a resonator is proposed. In an examination using a transistor Colpitts oscillator, the simulation using this technique agreed with the experimental results very well.