A new oxygen/nitrogen gas concentration sensor is described in this paper. This new sensor is based on the permselectivity of a membrane element. It is especially suited for the very low price market to determine the concentration of binary or pseudo-binary gas mixtures in the 0¿100% range.
The sensor is made of a permselective membrane module whose permeate stream is linked to a needle valve. The feed composition is related to the permeate build-up pressure, measured using a pressure transducer. Poly(dimethylsiloxane) (PDMS) and poly(etherimide) (PEI) hollow fiber membranes were tested. The response curves for both membranes at different temperatures display a quasi-linear behavior. The PDMS membrane-based sensor enables continuous and rapid oxygen analysis (t0¿95% = 50 s) with a reproducible and long-term stable signal ((O2) = 2.474 × 10¿6 dm3 (STP) s¿1 m¿2 Pa¿1, s = 0.045 × 10¿6, N = 10; (N2) = 1.173 × 10¿6 dm3 (STP) s¿1 m¿2 Pa¿1, s = 0.010 × 10¿6, N = 11) over 5.4 × 106 s. The absolute sensitivity of the PDMS-based sensor depends on the oxygen feed concentration ranging from 0.0329 to 0.450 MPa.
A simple analytical model was developed and is presented here. Good agreement was obtained with the experimental results for both membranes.
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