When talking aerospace sensors, ‘analogue’ or ‘digital’ become hardly necessary, being simply a matter of method of operation, and that it is the actual physical principles that are all-important.
Classification of sensors. In discussing sensing devices one has to decide if you should classify them in accordance with the physical property they use (including piezoelectric, photovoltaic, etc.) or according to 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 just a little disconcerting when one desires to compare the merits of, say, two types 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 and differentiate devices by function often tends to be an extremely boring catalogue of numerous unrelated devices. The important thing about the subject is signals are transformed from one form to a different. Additionally it is possible to discuss Torque Sensor from the functional viewpoint, under headings including length, temperature, etc., suitable for somebody that actually desires to select or use a sensor for the application as opposed to just read around the subject.
The text ‘sensors’ and ‘transducers’ are both widely used in the description of measurement systems. The previous is popular in the USA whereas the latter is much more often utilized 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 can lead to considerable ambiguity and misunderstanding, and is likely to diminish the preciseness from the language. The matter continues to be very apparent inside the computer and microprocessor areas, where preciseness is especially important, and will seriously confuse persons entering the niche.
The term ‘sensor’ comes from sentire, meaning ‘to perceive’ and ‘transducer’ comes from transducere meaning ‘to lead across’. A dictionary definition Chambers 20th Century of ‘sensor’ is ‘a device that detects a change in a physical stimulus and turns it right into a signal which is often measured or recorded’; a corresponding concept of ‘transducer’ is ‘a device that transfers power in one system to another inside the same or in different form’.
A sensible distinction is to use ‘sensor’ for your sensing element itself, and ‘transducer’ for that sensing element plus any associated circuitry. As an example, thermistors are sensors, since they respond to a stimulus (changes its resistance with temperature), but only become transducers when connected in a bridge circuit to transform improvement in potential to deal with improvement in voltage, because the complete circuit then transduces from your thermal to the electrical domain. A solar cell is both a sensor along with a transducer, since it responds to your stimulus (produces a current or voltage in reaction to radiation) as well as transducer from your radiant to the electrical domain. It can not require any associated circuitry, though in practice an amplifier would usually be applied. All transducers thus include a sensor, and lots of (though not all) sensors are also transducers.
The difference is rather small, and the moment one actually uses a sensor (by making use of capacity to it) it becomes Miniature Force Sensor. An appealing classification of devices can be accomplished by considering the various hdjjdy of energy or signal transfer.
The word ‘actuate’ means ‘to placed 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 may be of course transducers employed for output purposes, given that they transduce from one domain to another (ie. electrical to radiant for LEDs).