NPTEL – Mechanical – Mechatronics and Manufacturing Automation
Module 2: Sensors and signal processing
Sensors and transducers
Measurement is an important subsystem of a mechatronics system. Its main function
is to collect the information on system status and to feed it to the micro-processor(s)
for controlling the whole system.
Measurement system comprises of sensors, transducers and signal processing devices.
Today a wide variety of these elements and devices are available in the market. For a
mechatronics system designer it is quite difficult to choose suitable
sensors/transducers for the desired application(s). It is therefore essential to learn the
principle of working of commonly used sensors/transducers. A detailed consideration
of the full range of measurement technologies is, however, out of the scope of this
course. Readers are advised to refer “Sensors for mechatronics” by Paul P.L. Regtien,
Elsevier, 2012  for more information.
Sensors in manufacturing are basically employed to automatically carry out the
production operations as well as process monitoring activities. Sensor technology has
the following important advantages in transforming a conventional manufacturing
unit into a modern one.
1. Sensors alarm the system operators about the failure of any of the sub units of
manufacturing system. It helps operators to reduce the downtime of complete
manufacturing system by carrying out the preventative measures.
2. Reduces requirement of skilled and experienced labors.
3. Ultra-precision in product quality can be achieved.
It is defined as an element which produces signal relating to the quantity being
measured . According to the Instrument Society of America, sensor can be defined
as “A device which provides a usable output in response to a specified measurand.”
Here, the output is usually an ‘electrical quantity’ and measurand is a ‘physical
quantity, property or condition which is to be measured’. Thus in the case of, say, a
variable inductance displacement element, the quantity being measured is
displacement and the sensor transforms an input of displacement into a change in
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