1. Introduction to Sensors and Actuators

2. Sensors
Sensor is a device that when exposed to a physical phenomenon (temperature, displacement, force etc) produces a proportional output signal (electrical, mechanical, magnetic etc)
The term transducer is often used synonymously with sensors

3. Difference between sensors and transducers
Sensor is a device that responds to a change in the physical phenomenon
Transducer is a device that converts one form of energy into another form of energy
Sensors are transducers when they sense one form of energy input and output in a different form of energy
Eg: a thermocouple responds to a temperature change (thermal energy) and outputs a proportional change in electromotive force (electrical energy)

4. Classification Sensors are classified by their measurement objectives
Sensors can also be classified as passive or active
Passive sensors, the power required to produce the output is provided by the sensed physical phenomenon itself (thermometer)
Active sensors require external power source (Strain gage)

5. Classification
Sensors are classified as analog or digital based on the type of output signal
Analog Sensor
Analog sensors produce continuous signals that are proportional to the sensed parameter
It requires analog to digital conversion before feeding to the digital controller
Digital Sensor
Digital sensors produce digital outputs that can be directly interfaced with the digital controller

6. Principle of Operation
Linear and Rotational Sensors
Acceleration Sensors
Force, Torque, and Pressure Sensor
Flow Sensors
Temperature Sensors
Proximity Sensors
Light Sensors
Smart Material Sensors
Micro and Nanosensors

9. Selection Criteria Response time Range Bandwidth Resolution Accuracy
Resonance
Operating Temperature
Deadband
Signal to Noise ratio
Range
Resolution
Accuracy
Precision
Sensitivity
Zero offset
Linearity
Zero Drift

10. Range
Difference between the maximum and minimum value of the sensed parameter
Resolution
The smallest change the sensor can differentiate.
For digital sensors, it is related to number of bits used
For analog sensors, it is limited by low-level electrical noise
Sensitivity
Ratio of change in output to a unit change of the input
For digital sensors, sensitivity is closely related to resolution
For analog sensors, sensitivity is the output slope vs. input line

11. Accuracy Precision Zero offset Linearity
Difference between the measured value and the true value
Precision
Ability to reproduce repeatedly with the given accuracy
Zero offset
Non zero value output for no input
Linearity
Percentage of deviation from the best fit linear calibration curve

12. Zero drift Response Time Bandwidth Resonance
The departure of the output from zero value over period of time for no input
Response Time
The time lag between the input and output
Bandwidth
Frequency at which output magnitude drops by 3 dB
Resonance
Frequency at which the output magnitude peak occurs

13. Operating temperature
The range in which the sensor performs as specified
Deadband
Range of input for which there is no output
Signal to noise ratio
Ratio between the magnitude of the signal and the noise at the output

14. Interfacing Sensors with Arduino Microcontroller
Attach one leg of LDR to 5V and another leg attach 110K
register with that leg of LDR connected to A0
Attach another leg of register to the ground

15. const int sensorMin = 0;      // sensor minimum, discovered through experiment const int sensorMax = 600;    // sensor maximum, discovered through experiment void setup() {   // initialize serial communication:   Serial.begin(9600);   } void loop() {   // read the sensor:   int sensorReading = analogRead(A0);   // map the sensor range to a range of four options:   int range = map(sensorReading, sensorMin, sensorMax, 0, 3);   

16. // do something different depending on the range value:
  switch (range) {   case 0:    // your hand is on the sensor     Serial.println("dark");     break;   case 1:    // your hand is close to the sensor     Serial.println("dim");     break;   case 2:    // your hand is a few inches from the sensor     Serial.println("medium");     break;   case 3:    // your hand is nowhere near the sensor     Serial.println("bright");     break;   }    delay(1);        // delay in between reads for stability }

17. Role of Sensors in IoT system
While the IoT represents the convergence of advances in miniaturization, wireless connectivity, increased data storage capacity and batteries, the IoT wouldn’t be possible without sensors
Sensors detect and measure changes in position, temperature, light, etc. and they are necessary to turn billions of objects into data-generating “things” that can report on their status, and in some cases, interact with their environment