Sensor

In Metrology, a sensor is a sensitive device placed in contact with the physical quantity, the object of measurement, that is, it represents the element compatible and capable of collecting information from the physical quantity in the measuring environment. In other words, a sensor is defined as an instrument, or a part of a measuring system, capable of detecting the value of a certain quantity. It is, therefore, the element of the system whose behavior is influenced by the variation of the quantity to be measured.

Each sensor is generally sensitive to several physical quantities, but its change of state is definitely more significant in relation to a specific quantity for which it has been realized, the others, unfortunately, produce undesired influence variations of the quantity to be measured.

It is possible to consider the sensor as a component of a transducer, which acquires a signal, or a physical quantity. Furthermore, a measurement chain can also use more than one sensor thus generating a multisensory system. The sensors can interact with the measurement system directly or by stimulus. In the direct mode, the sensor is sensitive to a quantity which is an intrinsic attribute of the system being measured: for example, a thermocouple is sensitive to temperature. In the stimulus mode, the sensor is sensitive to the response of the system being measured when it is stimulated by an appropriate source.

A measurement chain can also use more than one sensor, thus generating a multisensory system. The sensors can interact with the measurement system either directly or as a stimulus. In the direct mode, the sensor is sensitive to an intrinsic physical quantity of the measurement system: for example, a thermocouple is temperature-sensitive. In stimulus mode, the sensor is sensitive to the response of the measurement system when a suitable source stimulates it.

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