ABSTRACT
There are a number of different criteria that are used for classifying sensors; here is a nonexhaustive list: ∑ Physical or (bio)chemical effect/transduction principle ∑ Principal form of signals ∑ Measurand (primary input variable) ∑ Technology and material ∑ Application ∑ Size (nano, micro, milli, macro) ∑ Characteristics (sensitivity, accuracy, etc.) ∑ Cost The selection of the criteria is strongly dependent on the type of user. For students, it might be adequate to use the classification by principle. For application engineers, it may be desired to class the sensors by measurand or application. For development engineers, technology, size, cost, and characteristics might be more of interest. Classifying sensors according to the nature of the measured quantity provides the following categories: ∑ Physical sensors ∑ Chemical sensors ∑ Biological sensors For all of them the measurement principles can be of a physical, chemical, or biological nature. For example, the measurement of the concentration of a given gas using the shift in frequency of a resonator (due to a change in mass) is a chemical sensor based on the physical principle. If we look at the principal form of signals, we can distinguish seven classes: ∑ Mechanical ∑ Thermal ∑ Electrical ∑ Magnetic ∑ Radiant ∑ Chemical ∑ Biological A number of examples for each class are given in Table 10.1.
