When talking torque sensor, ‘analogue’ or ‘digital’ become hardly required, being simply a case of approach to operation, and that it is the underlying physical principles that are all-important.
Classification of sensors
In discussing sensing devices one has to decide whether or not to classify them in accordance with the physical property they utilize (including piezoelectric, photovoltaic, etc.) or based on the function they perform (including measurement of length, temperature, etc.). In the former case anybody can present a reasonably integrated view of the sensing process, but it is just a little disconcerting when one wishes to compare the merits of, say, two kinds of temperature sensors, if one has to look over separate sections on resistive, thermoelectric and semiconductor devices to create the comparison.
Alternatively, to attempt to differentiate devices by function often is commonly a relatively boring catalogue of numerous unrelated devices. The important thing about the subject is signals are transformed from one form to another. It is also possible to discuss miniature load cell from your functional viewpoint, under headings such as length, temperature, etc., ideal for somebody that actually wants to select or utilize a sensor for a particular application rather than just read across the subject.
The words ‘sensors’ and ‘transducers’ are generally commonly used in the description of measurement systems. The previous is popular in the us whereas the latter is more often found in Europe. Deciding on a words in science is rather important. In recent years we have seen a tendency to coin new words or to misuse (or misspell) existing words, and this can lead to considerable ambiguity and misunderstanding, and tends to diminish the preciseness of the language. The issue has been very apparent within the computer and microprocessor areas, where preciseness is especially important, and will seriously confuse persons entering the topic.
The phrase ‘sensor’ comes from sentire, meaning ‘to perceive’ and ‘transducer’ originates from transducere meaning ‘to lead across’. A dictionary definition Chambers 20th 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 concept of ‘transducer’ is ‘a device that transfers power in one system to another one in the same or even in different form’.
A smart distinction is by using ‘sensor’ for the sensing element itself, and ‘transducer’ for your sensing element plus any associated circuitry. For instance, thermistors are sensors, given that they reply to a stimulus (changes its resistance with temperature), only become transducers when connected in a bridge circuit to convert change in resistance to improvement in voltage, because the complete circuit then transduces from your thermal to the electrical domain. A solar cell is both a sensor as well as a transducer, since it responds to your stimulus (creates a current or voltage in response to radiation) and also transducer from your radiant towards the electrical domain. It does not require any associated circuitry, though in practice an amplifier would usually be applied. All transducers thus hkjrzk a sensor, and lots of (though its not all) sensors will also be transducers.
The difference is pretty small and the moment one actually works with a sensor (by using capacity to it) it will become load cell. An appealing classification of devices can be accomplished by thinking about the various forms of energy or signal transfer.
The phrase ‘actuate’ means ‘to put in, or incite to, action’ and actuators are devices that produce the display or observable output in a measurement system like a light-emitting diode (LED) or moving coil meter. These are of course transducers employed for output purposes, because they transduce in one domain to another one (ie. electrical to radiant for LEDs).