The document provides an overview of the Internet of Things (IoT), detailing its components such as sensors and actuators, their classifications, and operational characteristics. It outlines the importance of sensing in various applications across consumer and industrial IoT and emphasizes critical factors affecting sensor choice and actuator functionality. The content also includes course objectives, learning outcomes, and examination formats for a robotics and automation program at JSS Academy, Bangalore.

1. Introduction to Internet of Things (IoT)
Department of Robotics & Automation
JSS Academy of Technical Education, Bangalore-560060
(Course Code: 22ETC15H)

2. Books
• Sudip Misra, Anandarup Mukherjee, Arijit Roy, “Introduction to IoT”, Cambridge University Press
2021.
Reference
• S. Misra, C. Roy, and A. Mukherjee, 2020. Introduction to Industrial Internet of Things and
Industry 4.0. CRC Press.
• Vijay Madisetti and Arshdeep Bahga, “Internet of Things (A Hands-on-Approach)”,1st Edition,
VPT, 2014.
• Francis daCosta, “Rethinking the Internet of Things: A Scalable Approach to Connecting
Everything”, 1st Edition, Apress Publications, 2013.
https://onlinecourses.nptel.ac.in/noc22_cs53/preview
Further Learning
National Programme on Technology Enhanced Learning (NPTEL)

3. Course Learning Objectives
• List the salient features of sensors & transducers
• Differentiate between sensors and actuators
• Characterize sensors & Actuators

4. Course outcome (Course Skill Set)
CO2: Classify various sensors actuators.
At the end of the course, students will be able to,

5. Semester End Examination(SEE)
• The question paper shall be set for 100 marks.
• The duration of SEE is 03 hours.
• The question paper will have 10 questions.
• 2 questions per module. Each question is set for 20 marks.
• The students have to answer 5 full questions, selecting one full question from each module.
• The student has to answer for 100 marks and marks scored out of 100 shall be
proportionally reduced to 50 marks.

6. Internet of Things
Module 2: IoT sensing & Actuation

7. IoT Sensing and Actuation: Introduction, Sensors, Sensor Characteristics,
Sensorial Deviations, Sensing Types, Sensing Considerations, Actuators,
Actuator Types, Actuator Characteristics.
Reference
Textbook1: Chapter 5: 5.1 to 5.9
Module 2

8. • IoT applications involves sensing in one or the other form.
• All the applications in IoT, consumer IoT, an industrial IoT, or hobby-based deployments of IoT
solutions - sensing forms the first step.
• Actuation forms the final step
• The sensing and actuation is based on the process of transduction.
• Transduction is the process of energy conversion.
• Transducers take energy in any form - electrical, mechanical, chemical, light, sound etc. & convert
it into other forms like electrical, mechanical, chemical, light, sound etc.
• Sensors and actuators are deemed as transducers.
• E.g., in a public announcement (PA) system, a microphone (input device) converts sound waves into electrical signals,
amplified by an amplifier system (a process). A loudspeaker (output device) outputs this into audible sounds by converting
the amplified electrical signals back into sound waves
IoT Sensing & Actuation

9. Differences between Transducers, Sensors, and Actuators
Parameter Transducer Sensor Actuator
Definition
Converts energy from
one form to another.
Converts various forms of energy
into electrical signals
Converts electrical signals into
various forms of energy.
Domain
Represent a sensor as
well as an actuator.
It is an input transducer. It is an output transducer
Function
Work as a sensor or an
actuator but not
simultaneously.
Used for quantifying environmental
stimuli into signals.
Used for converting signals
into proportional mechanical or
electrical outputs
Examples
Any sensor or
actuator
Humidity sensors, Temperature
sensors, Manometers, Gas sensors
etc.
Motors, Pumps etc.

10. Sensors
• Sensors are devices that can measure, or quantify, or respond to the ambient changes in
their environment.
• They generate responses to external or physical phenomenon and their conversion into
electrical signals.
• E.g., Heat is converted to electrical signals in a temperature sensor
Atmospheric pressure is converted to electrical signals in a barometer.

11. Sensors
A sensor is defined as a device, helps to detect any changes in physical quantity like pressure, force or
electrical quantity etc.

12. Industrial
IoT
Sensor
Systems
Industrial
IoT
Sensor
Systems

14. Outline of a Sensing Operation
• Temperature sensor keeps on checking an environment for changes.
• In the event of a fire, the temperature of the environment goes up.
• Temperature sensor senses this change in the temperature of the room and communicates this information
to a remote monitor via the processor
A sensor node is made up of a combination of sensor/sensors, a processor unit, a radio unit, and a power unit.

15. Classification of Sensors
3. Property to be measured
1. Active Sensor
2. Passive Sensor
1. Analog Sensor
2. Digital Sensor
The sensors are classified based on;
1. Power requirements
2. Sensor output
1. Scalar
2. Vector

16. Classification of Sensors
1. Active Sensor
2. Passive Sensor
1. Power requirements
1. Active Sensor: Do not require an external power source for their functioning.
E.g.: LiDAR (Light detection and ranging), Photoconductive cell, piezoelectric crystal etc.
2. Passive Sensor: Requires an external power source for their functioning.
E.g.: RTDs: Thermocouple

17. Classification of Sensors
1. Active Sensor
2. Passive Sensor
1. Power requirements

18. Classification of Sensors
1. Active Sensor
2. Passive Sensor
1. Power requirements
Thermocouple, Piezoelectric sensor etc. RTDs: Strain Gauge

19. Classification of Sensors
1. Analog Sensor
2. Digital Sensor
2. Sensor output
• Analogue sensors: Produce an analog output (continuous function of time).
• Digital Sensors: Work with discrete or digital data. Typically, binary output signals in the form of a logic 1
or logic 0 for ON or OFF.

20. Classification of Sensors
3. Property to be measured
1. Scalar
2. Vector
• Scalar: These sensors produce an output proportional to the magnitude of the quantity being measured.
• The output is in the form of a signal or voltage.
• E.g. colour, pressure, temperature, strain, gas, smoke, strain etc.
• Vector: Sensors are affected by both magnitude & direction and/or orientation of the property being measured.
• Velocity require additional information besides magnitude for completely describe the information.
• E.g. Sound sensor, image sensor, velocity sensor, acceleration sensor etc.

21. The functional blocks of a typical sensor node in IoT

22. Sensor Characteristics
1. Sensor Resolution
• The slightest/smallest change in the input (measurable quantity) that the sensor can detect.
• For digital sensors, the smallest change in the digital output
• More the resolution of a sensor, the more accurate.
• A sensor’s accuracy does not depend upon its resolution.
E.g. Temperature Sensor A can detect change in temperature up to 0:5°C;
Temperature Sensor B can detect change in temperature up to 0:25°C
Therefore, the resolution of sensor B is higher than the resolution of sensor A.

23. Sensor Characteristics
2. Sensor Accuracy
• Accuracy is the ability of a sensor to measure the changes in the environment of a system close to
its true value (Standard).
• E. g Weight sensor detects the weight of a 100 kg mass as 99.98 kg.
• We can say, this sensor is 99:98% accurate, with an error rate of 0:02%.
• Precision refers to the degree of reproducibility of a measurement.
• Exactly the same value were measured a no. of times (trials).
• An ideal sensor will provide am output exactly the same value every time.
E.g. If a pressure of exactly 150 mm Hg is applied to a sensor. Even if the applied pressure never changes, the
output values from the sensor will vary considerably.
3. Sensor Precision

24. Sensor Characteristics
4. Range
• Gives the highest and the lowest value of the physical quantity within which the sensor can actually
sense.
• Beyond these values, there is no sense or no kind of response.
• e.g. RTD for measurement of temperature has a range of -200`c to 800`c
• The ratio of incremental change in the response of the system wrt incremental change in input.
• It is the smallest amount of difference in quantity (i/p) that will change the instrument’s reading.
5. Sensitivity

25. Sensorial Deviations / Errors
• Sensor deviations are referred to as errors in sensors.
• Sensing in IoT is non-critical, where minor deviations in sensor outputs rarely changes the nature of
the undertaken tasks (applications).
• The critical applications of IoT, such as healthcare, industrial process monitoring, etc., require sensors
with high-quality measurement capabilities.

26. 1. Full Scale Range (Sensor limits): When sensor’s output is beyond its maximum and minimum design
capacity, the sensor output is truncated to its maximum or minimum value.
• The measurement range between minimum and maximum values is referred to as the full-scale range of
the sensor.
2. Offset / Bias: If the output signal is not zero when the measured property(i/p) is zero, the sensor has an
offset or bias error.
3. Non Linearity: If the sensitivity is not constant over the range of the sensor, this is called nonlinearity.
• Defined by the amount the output differs from ideal behaviour over the full range of the sensor
• Expressed as percentage of the full range.
Sensorial Deviations / Errors

27. 4. Dynamic Error: If the deviation is caused by a rapid change of the measured property over time.
5. Drift: If the output signal of a sensor changes slowly and independently of the measured property.
6. Hysteresis Error: if a sensor’s output varies/deviates due to deviations in the sensor’s previous input
values, it is referred to as hysteresis error.
• Generally denoted as a positive and negative percentage variation of the full-range of that sensor.
1. Quantization Error: If the digital output of a sensor is an approximation of the measured property.
• Defined as the difference between the actual analog signal and its closest digital approximation during
the sampling stage of the ADC.
Sensorial Deviations: Digital Sensors
Sensorial Deviations / Errors

28. • Dynamic Error caused due to mishandling of sampling frequencies can give rise to aliasing errors.
• Aliasing error leads to different signals of varying frequencies to be represented as a single signal in
case the sampling frequency is not correctly chosen, resulting in the input signal becomes a multiple of
the sampling rate.
Sensorial Deviations: Digital Sensors
Environment
• Some sensors may be prone to external influences.
• This sensitivity of the sensor may lead to deviations in its output values.
• E.g., Most sensors are semiconductor based, they are influenced by the temperature of their environment.

29. Sensing Types
Sensing can be divided into four different categories based on the nature of the environment
being sensed and the sensors being used;
1. Scalar sensing
2. Multimedia sensing
3. Hybrid sensing
4. Virtual sensing

30. Sensing Types
1. Scalar sensing
• Encompasses the sensing of features that can be quantified by measuring changes in the amplitude
(magnitude) of the measured values with respect to time.
• Measuring the changes in their values with time provides enough information about these quantities
• E.g., Ambient temperature, current, atmospheric pressure, rainfall, light, humidity, flux.
• A scalar temperature sensing of a fire detection event is shown in Fig.

31. Sensing Types
2. Multimedia sensing
• Encompasses the sensing of features that have a spatial variance property associated with the property
of temporal variance.
• Multimedia sensors are used for capturing the changes in amplitude of a quantifiable property
concerning space (spatial) as well as time (temporal).
E.g. Images, direction, flow, speed, acceleration, sound, force, mass, energy, and momentum
• A camera-based multimedia sensing using surveillance as an example is shown in Fig.

32. Sensing Types
3. Hybrid sensing
• The act of using scalar & multimedia sensing at the same time is referred to as hybrid sensing.
• Various sensors are employed (scalar & multimedia sensors) to measure the various properties of
the environment at any instant of time, and temporally map the collected information to generate new
information.
• E.g: Smart parking systems, traffic management systems etc.
• Fig. shows an example of hybrid sensing, where a camera and a temperature sensor are collectively
used to detect and confirm forest fires during wildlife monitoring.

33. Sensing Types
3. Hybrid sensing
Example: Agricultural field.
• It is required to measure the soil conditions at regular intervals of time to determine plant health.
• Soil moisture & temperature sensors are deployed underground to estimate the soil’s water retention
capacity and the moisture being held by the soil at any instant of time.
• This setup only determines whether the plant is getting enough water or not.
• There are other factors besides water availability, which may affect a plant’s health.
• The inclusion of a camera sensor with the plant, will determine the actual condition of a plant by
determining the colour of leaves.
• This information from soil moisture, temperature, and the camera sensor will be able to collectively
determine a plant’s health at any instant of time.
.

34. Sensing Types
4. Virtual sensing
• There is a need for very dense and large-scale deployment of sensor nodes spread over a large area for
monitoring of parameters.
• E.g. Agriculture
• The parameters being measured, are soil moisture, soil temperature, and water level, do not show significant
spatial variations.
• Sensors are deployed in the fields of farmer A, the measurements from the sensors will provide almost
concise measurements of his neighbour B’s fields; (fields which are surrounding A’s fields).
• If the data from A’s field is digitized using an IoT infrastructure and this system advises him regarding the
appropriate watering, fertilizer, and pesticide regimen for his crops, this advisory can also be used by B for
maintaining his crops.
• In short, A ’s sensors are being used for actual measurement of parameters; whereas virtual data is being
used for advising B.

35. Sensing Types
4. Virtual sensing
• Figure shows an example of virtual sensing.
• Two temperature sensors S1 and S3 monitor three nearby events E1, E2, and E3 (fire).
• The event E2 does not have a dedicated sensor for monitoring it; however, through the superposition of
readings from sensors S1 and S3, the presence of fire in E2 is inferred.

36. Sensing Considerations
• The choice of sensors in an IoT sensor node is critical and can either make or break the
feasibility of an IoT deployment.
• The major factors influence the choice of sensors in IoT-based sensing solutions:
1. Sensing range
2. Accuracy & precision
3. Energy
4. Device size

37. Sensing Considerations
1. Sensing Range
• The sensing range of a sensor may be used to signify the upper and lower bounds of a sensor’s
measurement range.
Example: A proximity sensor has a typical sensing range of a couple of meters.
• A camera has a sensing range varying between 10 meters to 100 meters.
• As the complexity of the sensor and its sensing range goes up, its cost significantly increases.

38. Sensing Considerations
2. Accuracy & Precision
• Accuracy and precision of measurements provided by a sensor are critical in deciding the operations of
specific functional processes.
• Consumer sensors are low on requirements & their performance is limited to regular application domains.
Example:
• A standard temperature sensor is not suitable for industrial processes.
• Regular temperature sensors have a very low-temperature sensing range & relatively low accuracy and
precision.
• The industrial applications requires precision of up to 3 - 4 decimal places
• Industrial sensors are very sophisticated, and are very costly.
• Industrial sensors have very high accuracy and precision, even under harsh operating conditions.

39. Sensing Considerations
3. Energy
• The energy consumed by a sensor / sensor node is crucial to determine the lifetime of that solution and
the estimated cost of its deployment.
• If the sensor / sensor node is energy inefficient, it requires replenishment of its energy sources
frequently, the effort in maintaining the solution and its cost goes up & its deployment feasibility goes
down.

40. Sensing Considerations
4. Device Size
• Modern-day IoT applications have a wide penetration in all domains of life.
• Most of the applications of IoT require sensing solutions which are so small that they do not hinder any of
the regular activities.
• Larger the size of a sensor node, larger is the obstruction caused by it, higher is the cost and energy
requirements, and lesser is its demand for the bulk of the IoT applications.
Example: Human activity detector.
• If the detection unit is large / bulky to be carried, cause hindrance to regular movements, the demand for this solution
would be low.
• The wearable sensors are highly energy-efficient & small in size.

41. Actuators

42. ACTUATORS
• An actuator is a component of a machine that is responsible for moving and controlling a
mechanism or system. E.g.: opening a valve.
• An actuator requires a control device (controlled by control signal) and a source of energy.
• The control signal may be electric voltage or current, pneumatic, or hydraulic fluid pressure, or
human power.
• The control device is usually a valve. When it receives a control signal, an actuator responds by
converting the source's energy into mechanical motion.
Outline of a simple actuation mechanism

43. Actuator Types
Broadly, actuators can be divided into seven classes:
1. Hydraulic
2. Pneumatic
3. Electrical
4. Thermal / Magnetic
5. Mechanical
6. Soft
7. Shape memory polymers

44. Actuator Types
Fig. shows some of the commonly used actuators in IoT applications

45. Actuator Types
• A works on the principle of compression and decompression of fluids.
• These actuators facilitate mechanical tasks such as lifting loads through the use of hydraulic
power derived from fluids.
• The mechanical motion applied to a hydraulic actuator is converted to either linear, rotary, or
oscillatory motion.
• used when exerting significant force.
• The actuator’s limited acceleration restricts its usage.
Hydraulic Actuator

46. Actuator Types
Pneumatic Actuator
• Pneumatic actuators use the energy of compressed air to generate rotary and linear movements to
operate valves and dampers
• Characteristics: Quick response to starting and stopping signals.
• Small pressure changes can be used for generating large forces. E.g. Pneumatic brakes.
• Pneumatic actuators are responsible for converting pressure into force.

47. Actuator Types
Electrical Actuator
• Electric actuators convert electrical energy into mechanical energy.
• Applications: Valve operation, cutting equipment, food and beverage manufacturing, and material
handling.
• Easy to maintain and offer a high level of precision.
• Not suited for all environments and need supervision for overheating tendencies.

48. Actuator Types
Thermal / Magnetic Actuator
• Thermal or magnetic energy is used.
• Have a very high power density and are compact, lightweight, and economical.
Example: Shape memory alloys (SMAs).
• These actuators do not require electricity for actuation.
• They are not affected by vibration and can work with liquid or gases.
• Magnetic shape memory alloys (MSMAs) are a type of magnetic actuators.
Magnetic technology for the Motor

49. Actuator Types
Mechanical Actuator
• In mechanical actuation, the rotary motion of the actuator is converted into linear motion.
• The use of gears, rails, pulleys, chains, etc. are necessary for these actuators to operate.
• These actuators can be easily used in conjunction with pneumatic, hydraulic, or electrical actuators.
• They can also work in a standalone mode.
Driving a pump actuator device (Linear) Rotary Actuator

50. Actuator Types
Soft Actuator
• Polymer-based consists of elastomeric polymers, used as embedded fixtures in flexible materials such
as cloth, paper, fiber, particles, etc.
• The conversion of molecular level microscopic changes into macroscopic deformations is the primary
working principle.
• These actuators have a high stake in modern-day robotics. They are designed to handle fragile
objects such as agricultural fruit harvesting, or performing precise operations like manipulating the
internal organs during robot-assisted surgeries.

51. Actuator Types
Shape Memory Polymers
• Shape memory polymers (SMP) are smart materials that respond to some external stimulus by
changing their shape, and then revert to their original shape once the affecting stimulus is removed.
• Characteristics: high strain recovery, biocompatibility, low density, and biodegradability.
• Modern-day SMPs, designed to respond to a wide range of stimuli such as pH changes, heat
differentials, light intensity, and frequency changes, magnetic changes, etc.
Example: Photopolymer/light-activated polymers (LAP), which require light as a stimulus to operate.

52. Actuator Characteristics
• The selection of actuators is crucial in an IoT deployment, where a control mechanism is required after
sensing and processing of the information obtained from the sensed environment.
• Actuators perform the physically heavier tasks in an IoT deployment; tasks which require moving or
changing the orientation of physical objects, changing the state of objects, etc.
• The correct choice of actuators is necessary for the long-term sustenance and continuity of operations, as
well as for increasing the lifetime of the actuators themselves.

53. Actuator Characteristics
• A set of four characteristics can define all the actuators:
1. Weight
2. Power Rating
3. Torque to Weight Ratio
4. Stiffness and Compliance

54. Actuator Characteristics
1. Weight: The physical weight of actuators limits its application scope.
Example
• Use of heavier actuators is generally preferred for industrial applications and applications
requiring no mobility of the IoT deployment.
• Lightweight actuators typically find common usage in portable systems in vehicles, drones,
and home IoT applications.
• Heavier actuators also have selective usage in mobile systems, for e.g., landing gears and
engine motors in aircraft.

55. Actuator Characteristics
2. Power Rating
• Helps in deciding the nature of the application.
• Power rating defines the minimum and maximum operating power an actuator can safely withstand without
damage to itself.
• Generally, it is indicated as the power-to-weight ratio for actuators.
Example
• Smaller servo motors used in hobby projects, have a maximum rating of 5 VDC, 500 mA, suitable for an
operations-driven battery-based power source.
• Exceeding this limit might be detrimental to the performance of the actuator and may cause burnout of the
motor.
• Servo motors in larger applications have a rating of 460 VAC, 2.5 A, requires standalone power supply
systems for operations.

56. Actuator Characteristics
3. Torque to Weight Ratio
• The ratio of torque to the weight of the moving part of an instrument/device is referred to
as its torque/weight ratio.
• This indicates the sensitivity of the actuator.
• Higher is the weight of the moving part; lower will be its torque to weight ratio for a given
power.

57. Actuator Characteristics
4. Stiffness and Compliance:
• The resistance of a material against deformation is known as its stiffness.
• Compliance of a material is the opposite of stiffness.
• Stiffness can be directly related to the modulus of elasticity of that material.
• Stiff systems are considered more accurate than compliant systems as they have a faster
response to the change in load applied to it.
Example
• Hydraulic systems are considered as stiff and non-compliant, whereas pneumatic systems are
considered as compliant.

58. End of Module