20ME702– MECHATRONICS -UNIT-1-Sensor and transducers.ppt
1.
2. Sensor
Sensor are devices which produce a
proportional output signal
(mechanical, electrical, magnetic etc.,)
when exposed to a physical
phenomenon (pressure, temperature,
displacement , force etc.,).
4. Performance terminology
• Static characteristics
– Static characteristics of an instrument are the
parameters which are more or less constant or varying
very slowly with time.
• Dynamic characteristics
– Sensors and actuators respond to inputs that change
with time. Dynamic characteristics of an instrument are
the parameters which are varying with time.
5. Static characteristics
Range – e.g.: a thermocouple may have a range of -100
to 1000°C
Span : maximum value of input – minimum value of
input
Error : measured value – true input value
Accuracy :
Sensitivity: it is defined as the change in output per
change in input
6. Static characteristics
Hysteresis: it is defined as the maximum difference
in output for a given input when this value is
approached from the opposite direction.
Linearity: it is refer to the output that is directly
proportional to input over its entire range.
7. Static characteristics
• Repeatability: it is defined as the ability of the sensor
to give same output reading when the same input value
is applied repeatedly under the same operating
conditions.
• Reproducibility: it is defined as the degree of
closeness among the repeated measurements of the
output for the same value of input under the same
operating conditions at different times.
8. Static characteristics
Stability : it means the ability of the sensor to
indicate the same output over a period of time for a
constant input.
Dead time: it is the time taken by the sensor from the
application of input to begin its response and change.
Resolution: it is defined as the smallest change that
can be detected by a sensor
10. Displacement sensor
A displacement sensor is used to measure travel
range between where an object is and a reference
position. Displacement sensors can be used for
dimension measurement to determine an object's
height, thickness, and width in addition to travel
range.
Potentiometer sensor
Strain gauge sensor
Capacitive sensor
Inductive sensors (LVDT)
11. Potentiometer Displacement sensor
A potentiometer sensor measures the distance or displacement of an object in a linear
or rotary motion and converts it into an electrical signal.
Linear potentiometer
14. Strain gauge Displacement sensor
strain gauges to measure the deformation of a beam under load, and to measure the
pressure /Force.
Strain gauge with Wheatstone bridge circuit
21. Position sensors
position sensor is used for a sensor that gives a measure of the distance between a
reference point and the current location of the target
potentiometer
Capacitive sensor
Inductive sensor
Hall effect sensors
Photoelectric sensor
Optical encoder
22. Hall effect sensors
Hall effect sensors leverage magnetic fields to determine factors such as positioning,
proximity, displacement, speed, and current.
Principle of Hall effect
25. Temperature sensors
A temperature sensor is a device that is designed to measure the degree of hotness or
coolness in an object.
Bimetallic strips
Resistance temperature detectors (RTDs)
Thermistors
Thermocouples
Thermodiodes and transistors