And Its Application
By farzi faraz
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.
a device that converts a primary form of energy into a
corresponding signal with a different energy forms.
a device that detect or measures a signal.
a device that generates a signal.
Class of sensors to measure mechanical
Force and torque sensor
Effect exhibited by various materials that exhibit a change in resistance
due to an applied pressure.
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
When stress is applied, the element and the SG is deformed at the
Gauge factor is defined as
Indicates how easy the strain can be measured
Large GF means large change in resistance for a given strain
the property of producing an electric charge when
subjected to an applied mechanical force.
Effect arises because of the charge asymmetry within the
Quartz and Rochelle salt are naturally occurring
The displacement measurement due to the change in capacitance.
There are 3 ways to change capacity
variation of plate separation
variation of plate area
variation of dielectric constant
a motion of permeable core changes the inductance
AC bridge can be used to detect the change in inductance
A resonator is a mechanical structure designed to vibrate at a
particular resonant frequency.
Pressure sensor is use to measure the pressure of fluid and gas in
Principles Involves Are
Pressure is force per area that fluid exerts on its surroundings
The fluid is not moving
The fluid is moving
P P gh 2 1
P v gy P v gy =constant
1 1 1 2 2 2
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
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.
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
Rotary torque sensors use rotary transducers to measure torque.
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.
A flow sensor is a device for sensing the rate of flow of
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
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
Microphones are a particular type of MEMS pressure
sensor designed to transduce acoustic signals into
electrical output. example hearing aid
Pressure sensor application in auto parts
sensor Auto parts applications
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
Torquemeter is a device for measuring and recording the torque
on a rotating system, such as an engine, crankshaft, gearbox
In control systems when motion feedback is employed.
In process testing, monitoring and diagnostics applications.
In measurement of power transmitted through a rotating
In controlling complex non-linear mechanical systems.
Application of inertial sensor
In industrial application, the design of accelerometer is
based on Newton’s Law and Hooke’s Law of Spring
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.
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 is the measurement of the velocity of fluids.
For measuring velocity and length on moving surfaces, laser surface
velocimeters are used.