Designing the measurement cell of a swept-field differential aspiration condenser

We present the description of a small-size and low-cost sensor based on the aspiration method that can be used as an ion-mobility spectrometer: the planar swept-field first-order differential aspiration condenser. A mathematical model for the measurement cell of the condenser has been developed, and in this paper a design strategy based on the model is described. A measurement cell has been constructed following this strategy and was used in a prototype aspiration condenser device. Some collector-plate ion-current curves have been measured for gas samples with several different anesthetic gases in different concentrations in order to evaluate the model and the design of the measurement cell. The inverse transform via the truncated singular value decomposition (TSVD) has been applied to the data to obtain ion-mobility spectra. The results suggest that, although the model simplifies the actual physical behavior of the ions, thereby causing some inconsistencies in the mobility spectra, it is still useful in the aspiration condenser's design process. The proposed device is an attractive small-size, cost-effective alternative for ion-mobility gas analysis applications.