Sensors
A sensor is a type of transducer, or mechanism, that responds to a
type of energy by producing another type of energy signal, usually
electrical. They are either direct indicating (an electrical meter) or are
paired with an indicator (perhaps indirectly through an analog to digital
converter, a computer and a display) so that the value sensed is
translated for human understanding. Types of sensors include
electromagnetic, chemical, biological and acoustic. Aside from other
applications, sensors are heavily used in medicine, industry and robotics.
In order to act as an effectual sensor, the following guidelines
must be met:
- the sensor should be sensitive to the measured property
- the sensor should be insensitive to any other property
- the sensor should not influence the measured property
In
theory, when the sensor is working perfectly, the output signal of a
sensor is exactly proportional to the value of the property it is meant to
measure. The gain is then defined as the ratio between output signal and
measured property. For example, if a sensor measures temperature and has
an actual voltage output, the gain is a constant with the unit.
When the sensor is not perfect, various deviations can occur,
including gain error, long term drift, and noise. These and other
deviations can be classified as systematic, or random, errors. Systematic
deviations may be compensated for by means of some kind of calibration
strategy. Noise is an example of a random error that can be reduced by
signal processing, such as filtering, usually at the expense of the
dynamic behavior of the sensor.
Continued >
By Jennifer-Lynn
Jennings
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