Introduction to IOT 21ETC151
MODULE-2
IOT SENSING AND ACTUATION
INTRODUCTION
A major chunk of IoT applications involves sensing in one form or the other. Almost all
the applications in IoT—be it a consumer IoT, an industrial IoT, or just plain hobby-
based deployments of IoT solutions—sensing forms the first step.
Actuation forms the final step in the whole operation of IoT application deployment in a
majority of scenarios.
The basic science of sensing and actuation is based on the process of transduction.
Transduction is the process of energy conversion from one form to another.
A transducer is a physical means of enabling transduction. Transducers take energy in
any form (for which it is designed)—electrical, mechanical, chemical, light, sound, and
others—and convert it into another, which may be electrical, mechanical, chemical, light,
sound, and others.
Sensors and actuators are deemed as transducers.
For example, in a public announcement (PA) system, a microphone (input device)
converts sound waves into electrical signals, which is amplified by an amplifier system (a
process). Finally, a loudspeaker (output device) outputs this into audible sounds by
converting the amplified electrical signals back into sound waves.
Differences between transducers, sensors, and actuators
Parameters Transducers Sensors Actuators
Definition Converts energy from Converts various forms of Converts electrical signals
one form to another energy into electrical into various forms of
signals. energy, typically
mechanical energy.
Domain Can be used to It is an input transducer. It is an output transducer
represent a sensor as
well as an actuator.
Function Can work as a sensor Used for quantifying Used for converting
or an actuator but not environmental stimuli into signals into proportional
simultaneously signals. mechanical or electrical
outputs.
Examples Any sensor or Humidity sensors, Motors (convert electrical
actuator Temperature sensors, energy to rotary motion),
Anemometers (measures Force heads (which
DEPT OF ECE,AJIET Page 1
, Introduction to IOT 21ETC151
flow velocity), impose a force), Pumps
Manometers (measures (which convert rotary
fluid pressure), motion of shafts into
Accelerometers (measures either a pressure or a fluid
the acceleration of a velocity).
body), Gas sensors
(measures concentration
of specific gas or gases),
and other
SENSORS
Sensors are devices that can measure, or quantify, or respond to the ambient changes in
their environment or within the intended zone of their deployment. They generate
responses to external stimuli or physical phenomenon through characterization of the
input functions (which are these external stimuli) and their conversion into typically
electrical signals.
For example, heat is converted to electrical signals in a temperature sensor, or
atmospheric pressure is converted to electrical signals in a barometer.
A sensor is only sensitive to the measured property (e.g., a temperature sensor only
senses the ambient temperature of a room).
It is insensitive to any other property besides what it is designed to detect (e.g., a
temperature sensor does not bother about light or pressure while sensing the
temperature).
a sensor does not influence the measured property (e.g., measuring the temperature does
not reduce or increase the temperature).
Figure 2.1 shows the simple outline of a sensing task. Here, a temperature sensor keeps
on checking an environment for changes. In the event of a fire, the temperature of the
environment goes up. The temperature sensor notices this change in the temperature of
the room and promptly communicates this information to a remote monitor via the
processor.
DEPT OF ECE,AJIET Page 2
, Introduction to IOT 21ETC151
Fig 2.1 The outline of a simple sensing operation
The various sensors can be classified based on:
1. power requirements,
2. sensor output, and
3. property to be measured.
Power Requirements:
The way sensors operate decides the power requirements that must be provided for an
IoT implementation.
Some sensors need to be provided with separate power sources for them to function,
whereas some sensors do not require any power sources.
Depending on the requirements of power, sensors can be of two types.
i) Active:
Active sensors do not require an external circuitry or mechanism to provide it with
power.
It directly responds to the external stimuli from its ambient environment and converts
it into an output signal.
For example, a photodiode converts light into electrical impulses. ‘
ii) Passive:
Passive sensors require an external mechanism to power them up.
The sensed properties are modulated with the sensor’s inherent characteristics to
generate patterns in the output of the sensor.
For example, a thermistor’s resistance can be detected by applying voltage difference
across it or passing a current through it.
Output:
The output of a sensor helps in deciding the additional components to be integrated with
an IoT node or system. Typically, almost all modern-day processors are digital; digital
sensors can be directly integrated to the processors.
The integration of analog sensors to these digital processors or IoT nodes requires
additional interfacing mechanisms such as analog to digital converters (ADC), voltage
level converters, and others.
Sensors are broadly divided into two types, depending on the type of output generated
from these sensors, as follows.
i) Analog:
Analog sensors generate an output signal or voltage, which is proportional (linearly or
non-linearly) to the quantity being measured and is continuous in time and amplitude.
Physical quantities such as temperature, speed, pressure, displacement, strain, and
others are all continuous and categorized as analog quantities.
DEPT OF ECE,AJIET Page 3
MODULE-2
IOT SENSING AND ACTUATION
INTRODUCTION
A major chunk of IoT applications involves sensing in one form or the other. Almost all
the applications in IoT—be it a consumer IoT, an industrial IoT, or just plain hobby-
based deployments of IoT solutions—sensing forms the first step.
Actuation forms the final step in the whole operation of IoT application deployment in a
majority of scenarios.
The basic science of sensing and actuation is based on the process of transduction.
Transduction is the process of energy conversion from one form to another.
A transducer is a physical means of enabling transduction. Transducers take energy in
any form (for which it is designed)—electrical, mechanical, chemical, light, sound, and
others—and convert it into another, which may be electrical, mechanical, chemical, light,
sound, and others.
Sensors and actuators are deemed as transducers.
For example, in a public announcement (PA) system, a microphone (input device)
converts sound waves into electrical signals, which is amplified by an amplifier system (a
process). Finally, a loudspeaker (output device) outputs this into audible sounds by
converting the amplified electrical signals back into sound waves.
Differences between transducers, sensors, and actuators
Parameters Transducers Sensors Actuators
Definition Converts energy from Converts various forms of Converts electrical signals
one form to another energy into electrical into various forms of
signals. energy, typically
mechanical energy.
Domain Can be used to It is an input transducer. It is an output transducer
represent a sensor as
well as an actuator.
Function Can work as a sensor Used for quantifying Used for converting
or an actuator but not environmental stimuli into signals into proportional
simultaneously signals. mechanical or electrical
outputs.
Examples Any sensor or Humidity sensors, Motors (convert electrical
actuator Temperature sensors, energy to rotary motion),
Anemometers (measures Force heads (which
DEPT OF ECE,AJIET Page 1
, Introduction to IOT 21ETC151
flow velocity), impose a force), Pumps
Manometers (measures (which convert rotary
fluid pressure), motion of shafts into
Accelerometers (measures either a pressure or a fluid
the acceleration of a velocity).
body), Gas sensors
(measures concentration
of specific gas or gases),
and other
SENSORS
Sensors are devices that can measure, or quantify, or respond to the ambient changes in
their environment or within the intended zone of their deployment. They generate
responses to external stimuli or physical phenomenon through characterization of the
input functions (which are these external stimuli) and their conversion into typically
electrical signals.
For example, heat is converted to electrical signals in a temperature sensor, or
atmospheric pressure is converted to electrical signals in a barometer.
A sensor is only sensitive to the measured property (e.g., a temperature sensor only
senses the ambient temperature of a room).
It is insensitive to any other property besides what it is designed to detect (e.g., a
temperature sensor does not bother about light or pressure while sensing the
temperature).
a sensor does not influence the measured property (e.g., measuring the temperature does
not reduce or increase the temperature).
Figure 2.1 shows the simple outline of a sensing task. Here, a temperature sensor keeps
on checking an environment for changes. In the event of a fire, the temperature of the
environment goes up. The temperature sensor notices this change in the temperature of
the room and promptly communicates this information to a remote monitor via the
processor.
DEPT OF ECE,AJIET Page 2
, Introduction to IOT 21ETC151
Fig 2.1 The outline of a simple sensing operation
The various sensors can be classified based on:
1. power requirements,
2. sensor output, and
3. property to be measured.
Power Requirements:
The way sensors operate decides the power requirements that must be provided for an
IoT implementation.
Some sensors need to be provided with separate power sources for them to function,
whereas some sensors do not require any power sources.
Depending on the requirements of power, sensors can be of two types.
i) Active:
Active sensors do not require an external circuitry or mechanism to provide it with
power.
It directly responds to the external stimuli from its ambient environment and converts
it into an output signal.
For example, a photodiode converts light into electrical impulses. ‘
ii) Passive:
Passive sensors require an external mechanism to power them up.
The sensed properties are modulated with the sensor’s inherent characteristics to
generate patterns in the output of the sensor.
For example, a thermistor’s resistance can be detected by applying voltage difference
across it or passing a current through it.
Output:
The output of a sensor helps in deciding the additional components to be integrated with
an IoT node or system. Typically, almost all modern-day processors are digital; digital
sensors can be directly integrated to the processors.
The integration of analog sensors to these digital processors or IoT nodes requires
additional interfacing mechanisms such as analog to digital converters (ADC), voltage
level converters, and others.
Sensors are broadly divided into two types, depending on the type of output generated
from these sensors, as follows.
i) Analog:
Analog sensors generate an output signal or voltage, which is proportional (linearly or
non-linearly) to the quantity being measured and is continuous in time and amplitude.
Physical quantities such as temperature, speed, pressure, displacement, strain, and
others are all continuous and categorized as analog quantities.
DEPT OF ECE,AJIET Page 3
