When talking torque transducer, ‘analogue’ or ‘digital’ become hardly required, being simply a matter of approach to operation, and that it must be the underlying physical principles which can be all-important.
Classification of sensors
In discussing sensing devices one must decide whether or not to classify them in accordance with the physical property they use (including piezoelectric, photovoltaic, etc.) or in accordance with the function they perform (such as measurement of length, temperature, etc.). Within the former case one can present a reasonably integrated look at the sensing process, but it is just a little disconcerting when one desires to compare the merits of, say, two kinds of temperature sensors, if one has to look through separate sections on resistive, thermoelectric and semiconductor devices to help make the comparison.
Alternatively, to try and differentiate devices by function often is usually a rather boring catalogue of numerous unrelated devices. The main thing about them is signals are transformed in one form to a different. It is also possible to discuss miniature load cell through the functional viewpoint, under headings like length, temperature, etc., appropriate for someone who actually wants to select or make use of a sensor for the application rather than just read round the subject.
The text ‘sensors’ and ‘transducers’ are both popular in the description of measurement systems. The former is popular in the USA whereas the latter is more often found in Europe. The option of words in science is rather important. In recent years there has been a tendency to coin new words or misuse (or misspell) existing words, and this may lead to considerable ambiguity and misunderstanding, and has a tendency to diminish the preciseness in the language. The matter has become very apparent in the computer and microprocessor areas, where preciseness is especially important, and will seriously confuse persons entering the topic.
The word ‘sensor’ is derived 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 may be measured or recorded’; a corresponding meaning of ‘transducer’ is ‘a device that transfers power in one system to another within the same or perhaps in different form’.
A smart distinction is by using ‘sensor’ for your sensing element itself, and ‘transducer’ for your sensing element plus any associated circuitry. For example, thermistors are sensors, because they reply to a stimulus (changes its resistance with temperature), but only become transducers when connected in a bridge circuit to transform improvement in effectiveness against change in voltage, considering that the complete circuit then transduces through the thermal to the electrical domain. A solar cell is both a sensor as well as a transducer, since it responds to a stimulus (creates a current or voltage in response to radiation) as well as transducer from your radiant to the electrical domain. It does not require any associated circuitry, though in reality an amplifier would usually be utilized. All transducers thus hkjrzk a sensor, and lots of (though not all) sensors will also be transducers.
The distinction is quite small and once one actually uses a sensor (by applying capacity to it) it might be load sensor. An appealing classification of devices can be achieved by thinking about the many forms 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 like a light-emitting diode (LED) or moving coil meter. They are obviously transducers employed for output purposes, given that they transduce from one domain to another (ie. electrical to radiant for LEDs).