Numeryczna korekcja dynamiki półprzewodnikowych czujników gazów

W artykule przedstawiono metodę oraz wyniki badań właściwości dynamicznych typowego półprzewodnikowego rezystancyjnego czujnika gazów. W oparciu o uzyskane wyniki zaproponowano model dynamiczny czujnika, wyznaczono jego współczynniki oraz przedstawiono dopasowaną do tego modelu numeryczną procedurę korekcji dynamicznej zapewniającą istotne skrócenie czasu odpowiedzi przetwornika do pomiaru stężenia gazu. Pokazano skuteczność zaproponowanej metody korekcji.

Solid state gas sensors have generally disadvantageous dynamic properties - their response time can reach several minutes or more. This is due to the fact that the chemical adsorption phenomena in the sensitive layer occur relatively slowly [1, 2]. In many measurement applications such a long response time is not acceptable. It is necessary to apply effective methods of dynamic correction. This paper presents a method and results of investigations of the dynamic properties of a typical semiconductor gas sensor with tin sensing layer. A numerical correction method is proposed, too. There were determined responses of the sensor to step changes in gas concentration by means of a measuring system shown schematically in Fig. 2. The results (see Figs. 3, 4 and 5) show that the first order inertia may be sufficient as an averaged dynamic model of the sensor. With respect to this model, the dynamic correction method is proposed. The procedure is illustrated in Fig. 6, and the calculation method is given in formula (3). Shortening of the step response time is expressed by the coefficient (0, 1). Examples of application of that algorithm to reproduce the abruptly and sinusoidally varying gas concentration are shown in Figs. 7 and 8 ( was assumed equal to 1/3, which was the postulated 3-fold reduction of the step response time). The waveforms confirm the effectiveness of the proposed dynamic correction method.