Gas sensor measurement system capable of sampling volatile organic compounds (VOCs) in wide concentration range

Abstract

A gas sensor measurement system has been developed by using a vapor-generating bubbler, analyte-diluted delivery lines and a detection chamber. The bubbler with a perforated disk design permits to pick up analyte vapor with fixed efficiency under a carrier flow rate of 0.5–100 sccm. The pickup efficiency was modulated logarithmically by varying the bubbler temperature. The practically controllable range in acetone flux was nearly three orders of magnitude through the variation of the carrier flow rate, and an order of magnitude by the use of the bubble temperature, independently. The generated vapor was diluted efficiently through a cascading two-step process which leads to homogeneous mixing up to the flow ratio of dilution:carrier = 500:0.25, and then delivered into a small-gapped planar detection chamber operated at room temperature. The newly-designed planar chamber induces fast equilibrium and high local concentration on a sensor surface, thus resulting in a short detection time and a higher response magnitude. From measuring chemoresistive responses of carbon black-polymer composites upon exposure to acetone analyte, the measurement system was confirmed to be reliably applicable to a wide concentration range of from 3.7 ppm to 10.7%.