Electrical Engineering


Metal Oxide Chemiresistors

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The metal oxide chemiresistor works, based on reduction of oxygen on the sensor surface by a reducing gas. In a standard environment, oxygen bonds to the surface of the metal-oxide sensor, extracting electrons from the bulk. A reducing gas will, in turn, bind with the oxygen, causing electrons to be re-injected into the bulk (resistance decreases). The most common metal oxide chemiresistor is made of tin oxide. It can be doped with various catalysts (such as palladium) to narrow the selectivity to some reducing gases over others.

The data contained in these pages use the 'metal_oxide' technology type and the function chemiresistor (located in the chemiresistor.m file on the previous page). Data are collected from the technical literature, from personal communications, from laboratories here at UW, and other sources. All available information regarding the experiments used to produce the data (and the corresponding models) are provided in each of the links above.

The basic metal oxide chemiresistor model for small concentrations assumes a power-law response to analyte concentration as follows:
R = A*([C]^m)
R = output resistance
A = constant that contains both baseline resistance and analyte/sensor dependent components
m = an analyte/sensor dependent constant
[C] = analyte concentration in ppm