Taguchi sensor

Fig. 4.48 (a) The classic Taguchi sensor (b) the typical screen-printed planar format. 

Conductimetric sensors - electrochemical sensors for which the electrical - conductivity of the sensor material is recorded. A typical example is the so-called - Taguchi sensor that is used for detection of reducing gases in air. Ref [i] Janata / (1989) Principles ofchemical sensors. Plenum, New York... 

Figure 31. The change in the ionic surface conductivity upon a variation in the partial pressure of the acidbase active gas (bottom) is analogous to the Taguchi sensor which works for redox-active gases.20...

Metal oxide semiconductor gas sensor (Taguchi sensor)... 

Jamnik, J., Kamp, B., Merkle, R. and Maier, J. (2002), Space charge inflnenced oxygen incorporation in oxides in how far does it contribnte to the drift of Taguchi sensors Solid State Ionics, 150(1-2), 157-66. 

Other groups, like El Barbri et al. [41], analyzed both beef and sheep meat (stored at 4°C for up to 15 days) by a laboratory EN based on Taguchi sensors aiming to develop a protocol for the quality control of red meat. The EN, coupled to SVM, could discriminate between unspoiled/ spoiled beef or sheep meats with a success rate above 96 %. Good correlation between the EN signals and the bacteriological data were also obtained. 

Ihokura K, Watson J (1994) The stannic oxide gas sensor—principles and applications. CRC Press, Boca Raton, FL Itoh T, Matsubara I, Shin W, Izu N, Nishibori M (2008) Analytical study of resistance drift phenomena on (PANHxMoO hybrid thin films as gas sensors. Bull Chem Soc Jpn 81(10) 1331-1335 Jamnik J, Kamp B, Merkle R, Maier J (2002) Space charge influenced oxygen incorporation in oxides in how far does it contribute to the drift of Taguchi sensors Solid State Ion 150 157-166... 

Humidity effect. Humidity often influences both the zero point of a Taguchi sensor and the sensitivity, which makes corrections difficult as shown in Figure 9. 

Table 1 demonstrates that this is the general behavior of semiconductor gas sensors. The slope of the calibration curve can vary by up to a factor of 5. In this table, three different Taguchi sensors (TGS 800. TGS 813, and TGS 822) were carefully compared [257] with respect to their humidity interference using ethanol as the analyte. 

The high T ceramic superconductors have been tested in Taguchi-type sensois. The Taguchi gas sensor is based on a semiconducting metal oxide, which exhibits a resistance change when gas molecules adsorb at the surface and influence the charge carrier concentration in the metal oxide. SnOj, lUjOj, and solid solutions based on these oxides have frequently been studied as active material of the Taguchi sensor. 

Example 3 (Fig. 5.70c) illustrates a solid-gas contact, more precisely the contact between the n-type semiconductor Sn02 with O2 gas. At low temperatiures the adsorbed oxygen cannot penetrate the interior, but remains adsorbed on the surface. It traps electrons from the boundary layer and makes this positively charged, producing a depletion layer of increased resistance. This is the basic principle of the Taguchi sensor, which we will discuss later. Such effects must also be discussed at elevated temperatmes when phase equilibrium with oxygen is established. 

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