Sensor

Definition of Sensor: A sensor is a device that converts a stimulus (e.g. heat, pressure or light) into a (in most cases electrical) signal that can be measured or interpreted. It is a part of an instrument or, in the context of this Wiki, an oceanographic instrument. This is the common definition for Sensor, other definitions can be discussed in the article

Often the word sensor is used synonymous to an oceanographic instrument.

Overview

In an oceanographic instrument the stimulus can either interact directly with the detector (such as in a temperature, pressure or light sensor) or a stimulus is exserted by the instrument, then is modified by the property to be measured and the modified stimulus then interacts with the detector (such as in a fluorometer that sends out a light pulse (stimulus) that is transformed by chlorophyll fluorescence in the water (modification of stimulus); the transformed light (modified stimulus) then is interacting with the detector).

If the detector signal is not an electrical signal (e.g. an optical signal or the change of a property such as colour) it can be converted to an electrical signal by a transducer. Detector and transducer together form the sensor.

Important properties

• Sensitivity: The smallest change in the property to be measured that leads to a measurable change in the detector signal.
• Selectivity: In how far the change of other properties than the one to be measured leads to a change in the detector signal. High selectivity sensors exhibit little influence of detector signal from changes in properties other than the one to be measured.
• Range: The span between the extremes of the property to be measured at which no further change in detector signal occurs.
• Linearity: A measure that represents in how far equal amounts of change in the property to be measured lead to equal amounts of change in detector signal.

Sensors and oceanographic instruments