This document discusses various types of mechanical sensors and their applications. It describes sensors that measure mechanical phenomena like pressure, force, torque, inertia, and flow. Pressure sensors are used in applications like manometers, barometers, microphones, and automotive parts. Force and torque sensors can be used in control systems, testing equipment, and for measuring power transmission. Inertial sensors like accelerometers have applications in industry, military, vibration monitoring, and safety systems. Flow sensors measure flow rates using principles of heat transfer and are used in microsensors and velocimetry applications. The document provides details on common sensing techniques like piezoresistivity, piezoelectricity, capacitive, inductive and resonant techniques.

1. Mechanical Sensor
And Its Application
By farzi faraz

2. What is sensor ?
 A sensor is a converter that measures a physical quantity
and converts it into a signal which can be read by an
observer or by an instrument.
 Example a mercury in glass thermometer.

3. Three terms
Transducer
a device that converts a primary form of energy into a
corresponding signal with a different energy forms.
Sensor
a device that detect or measures a signal.
Actuator
a device that generates a signal.
sensor intelligent
real
world actuator
feedback
system

4. Mechanical Sensor
 Class of sensors to measure mechanical
phenomena.
 Includes
Pressure sensor
Force and torque sensor
Inertial sensor
Flow sensor

5. Mechanical Sensing Techniques
 Piezoresistivity
 Piezoelectricity
 Capacitive techniques
 Inductive techniques
 Resonant techniques

6. Piezoresistivity
Effect exhibited by various materials that exhibit a change in resistance
due to an applied pressure.
Strain Gauge
Sensors that exhibit a change in resistance as a result of an applied
strain are generally termed strain gauges.
 The strain gauge (SG) is glued to the element whose strain is to be
measured
 When stress is applied, the element and the SG is deformed at the
same manner
 Gauge factor is defined as
R /
R


strain
GF
Indicates how easy the strain can be measured
Large GF means large change in resistance for a given strain
Strain gauge

7. Piezoelectricity
 the property of producing an electric charge when
subjected to an applied mechanical force.
 Effect arises because of the charge asymmetry within the
crystal structure.
 Quartz and Rochelle salt are naturally occurring
piezoelectric.
Applied force
Piezoelectric material

8. Capacitive Techniques
 The displacement measurement due to the change in capacitance.
 Capacitance
C  K

0
A
d
 There are 3 ways to change capacity
 variation of plate separation
 variation of plate area
 variation of dielectric constant

9. Inductive Techniques
 Inductance
 a motion of permeable core changes the inductance
 AC bridge can be used to detect the change in inductance
   BdS
s
L


i

10. Resonant Techniques
 A resonator is a mechanical structure designed to vibrate at a
particular resonant frequency.
Block Diagram

11. Pressure Sensor
 Pressure sensor is use to measure the pressure of fluid and gas in
industrial application.
Principles Involves Are
 Pressure is force per area that fluid exerts on its surroundings
 Static Pressure
 The fluid is not moving
 Dynamic Pressure
 The fluid is moving
P  P gh 2 1
1 1
2 2
2 2
P  v  gy  P  v  gy =constant
1 1 1 2 2 2

12. Pressure sensor
 Pressure sensor types
Absolute pressure sensor
sensor measures the pressure relative to perfect vacuum.
Gauge pressure sensor
sensor measures the pressure relative to atmospheric pressure.
Vacuum pressure sensor
sensor that measures pressures below atmospheric pressure.
Differential pressure sensor
sensor measures the difference between two pressures

13. Force and torque sensor
 The fundamental operating principles of force and torque sensor
instrumentation are closely allied to the piezoelectric and strain gage devices
used to measure static and dynamic pressures.
 Consider a simple sensor that is to be developed to measure a reaction force at
the base of a spring, as shown below.

14. Force and torque sensor
 Torque is a measure of the forces that causes an object to rotate.
 Reaction torque sensors measure static torque with a stationary or
non-rotating transducer.
 Rotary torque sensors use rotary transducers to measure torque.

15. Inertial Sensor
 Inertial sensor measures linear acceleration along one or
several axis refered to as accelerometer.
 Sensor that measures angular acceleration along one or
several axis are refered to as gyroscope.
accelerometer
gyroscope

16. Flow Sensor
 A flow sensor is a device for sensing the rate of flow of
material.
 Material may be solid liquid or gas.
 Flow rate is measured by weighting the amount of
material on a platform of length L
flow (kg/min or lb/min)
weight of material on section of length L (kg or lb)
conveyor speed (m/min, or ft/min)
length of weighting platform
Q
W
R
L




WR
Q
L


17. Application of different
mechanical sensor

18. Application OF Pressure Sensor
 Manometer a traditional pressure sensor.
Manometers can be used both as a gauge sensor with one side
vented to atmosphere and as differential sensors with pressure
applied to both legs.
Pressure sensor are also use in aneroid barometer and
bourdon tube.
 Microphones are a particular type of MEMS pressure
sensor designed to transduce acoustic signals into
electrical output. example hearing aid

19. Bourdon tube U tube manometer

20. Pressure sensor application in auto parts
sensor Auto parts applications

21. Application of force and torque sensor
 A force-sensing resistor is a material whose resistance changes
when a force or pressure is applied. They are also known as
forcesensitive resistor.
 Torquemeter is a device for measuring and recording the torque
on a rotating system, such as an engine, crankshaft, gearbox
etc
 In control systems when motion feedback is employed.
 In process testing, monitoring and diagnostics applications.
 In measurement of power transmitted through a rotating
device.
 In controlling complex non-linear mechanical systems.

22. torquemeter
Force sensitive resister

23. Application of inertial sensor
 Accelerometer
In industrial application, the design of accelerometer is
based on Newton’s Law and Hooke’s Law of Spring
ma  kx
spring constant in N/m
spring extension in m
mass in kg
acceleration in m/s
 Inertial sensors are used for military applications such as inertial
guidance and smart ammunition.
 Accelerometers can be used to measure vibration on cars, machines,
buildings, process control systems and safety installations.
2
k
x
m
a

 



24. accelerometer

25. Application of flow sensor
 flow sensors are based on sensors which measure the transfer of heat
caused by the moving medium. This principle is common for
microsensors to measure flow.
 Velocimetry
Velocimetry is the measurement of the velocity of fluids.
For measuring velocity and length on moving surfaces, laser surface
velocimeters are used.
velocimeter

26. THANK YOU