When talking aerospace sensors, ‘analogue’ or ‘digital’ become hardly necessary, being simply a matter of approach to operation, and that it is the actual physical principles that are all-important.
Classification of sensors. In discussing sensing devices one must decide whether or not to classify them based on the physical property they normally use (like piezoelectric, photovoltaic, etc.) or in accordance with the function they perform (such as measurement of length, temperature, etc.). Within the former case you can present a reasonably integrated take a look at the sensing process, but it is a bit disconcerting when one wishes to compare the merits of, say, two kinds of 3 Axis Load Cell, if one has to examine separate sections on resistive, thermoelectric and semiconductor devices to help make the comparison.
Alternatively, to try to differentiate devices by function often tends to be a relatively boring catalogue of numerous unrelated devices. The main thing about the subject is signals are transformed from one form to a different. It is also easy to discuss Torque Sensor from your functional viewpoint, under headings such as length, temperature, etc., appropriate for someone who actually desires to select or use a sensor for the application rather than just read across the subject.
The text ‘sensors’ and ‘transducers’ are both popular inside the description of measurement systems. The previous is popular in the us whereas the latter is more often found in Europe. The option of words in science is quite important. Recently there has been a propensity to coin new words or misuse (or misspell) existing words, and this might lead to considerable ambiguity and misunderstanding, and has a tendency to diminish the preciseness from the language. The matter has been very apparent inside the computer and microprocessor areas, where preciseness is particularly important, and may seriously confuse persons entering the subject.
The phrase ‘sensor’ hails from sentire, meaning ‘to perceive’ and ‘transducer’ originates from transducere meaning ‘to lead across’. A dictionary definition Chambers Twentieth Century of ‘sensor’ is ‘a device that detects a big difference in a physical stimulus and turns it into a signal which can be measured or recorded’; a corresponding definition of ‘transducer’ is ‘a device that transfers power from one system to another one inside the same or even in different form’.
A smart distinction is to apply ‘sensor’ for the sensing element itself, and ‘transducer’ for your sensing element plus any associated circuitry. For instance, thermistors are sensors, because they reply to a stimulus (changes its resistance with temperature), only become transducers when connected in a bridge circuit to transform alternation in effectiveness against change in voltage, since the complete circuit then transduces from the thermal to the electrical domain. A solar cell is both a sensor and a transducer, since it responds to your stimulus (produces a current or voltage responding to radiation) and in addition transducer from the radiant to the electrical domain. It will not require any associated circuitry, though in practice an amplifier would usually be used. All transducers thus have a sensor, and several (though not all) sensors will also be transducers.
The distinction is quite small, and the moment one actually works with a sensor (by applying power to it) it might be Jr S Beam Load Cell. An interesting classification of devices can be accomplished by taking into consideration the various hdjjdy of energy or signal transfer.
The phrase ‘actuate’ means ‘to put into, or incite to, action’ and actuators are devices that make the display or observable output in a measurement system for instance a light-emitting diode (LED) or moving coil meter. They are needless to say transducers employed for output purposes, since they transduce from a single domain to another one (ie. electrical to radiant for LEDs).