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.
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 in the instrument.
- 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.