explains about the sensors and its types.....

2. Sensors
 Sensors are sophisticated devices that are
frequently used to detect and respond to electrical
or optical signals. A Sensor converts the physical
parameter (for example: temperature, blood
pressure, humidity, speed, etc.) into a signal which
can be measured electrically.
 Sensors are made from silicon.

3. Features of a sensor
 Accuracy
 Environmental condition
 Range - Measurement limit of sensor
 level of Calibration
 Resolution
 Cost
 Repeatability

4. Classification of sensors
 Primary Input quantity (Measurand)
 Transduction principles (Using physical and
chemical effects)
 Material and Technology
 Property
 Application

5. Types of sensors
 Temperature
 IR Sensors
 UV Sensors
 Touch Sensor
 Proximity Sensor
 Smart Sensor

6. Smart sensor
 A smart sensor is a device that takes input from the
physical environment and uses built-in compute
resources to perform predefined functions upon
detection of specific input and then process data
before passing it on.
 It is a combination of both sensor and actuator.
[sensor + interfacing circuit = smart sensor]
 Capable of logic functions, two-way communication
and making decisions.
 Accuracy level is very high.

7. Classification of smart sensor
 Based on sensor
 Pressure Sensors
 Temperature & Humidity Sensors
 Flow Sensors
 Image Sensors
 Touch Sensors
Water Sensors
 Based on technology
 MEMS-based smart sensors
 CMOS-based smart sensors

8.  Based on Component:
 Analog To Digital Converters (ADCs)
 Digital To Analog Converters (DACs)
 Transceivers
 Amplifiers
 Microcontrollers
 Based on Network Connectivity:
 Wired
 Wireless

9. Properties of smart sensors
 Self calibration: Adjust deviation of output of sensor
from desired value.
 Communication: Broadcast information about its
own status.
 Computation: Allows one to obtain the average,
variance and standard deviation for the set of
measurements.
 Multi-sensing: A single smart sensor can measure
pressure, temperature, humidity, gas flow and infrared
chemical reaction surface acoustic vapour etc.
 Cost improvement: less hardware and reduction of
repetitive testing make smart sensor cost effective

10. Block diagram of smart sensors

11.  The sensor sense the object and it’s output is created in
the form of analog signals.
 Using the ADC ,the analog signal is converted in
digital signal.
 After the conversion the signal can be easily
transmitted.

12. Evolution of sensors
 First generation devices had little, if any, electronics
associated with them. Had MEMS sensor element
(mostly based on a silicon structure) and sometimes
combined with analog amplification on a micro chip.
 Second generation sensors were part of purely
analog systems with virtually all of the electronics
remote from the sensor. Had MEMS sensor element
combined with analog amplification and analog-to-
digital converter on one micro chip.

13. 3rd generation sensors
Fusion of the sensor element with analog amplification,
analog-to-digital converter and digital intelligence for
linearization and temperature compensation on the same
micro chip.

14. 4th generation sensors
 Memory cells for calibration and temperature
compensation data are added to the elements of
the 3rd MEMS sensor generation.

15. 5th generation sensors
 This generation sensors are equivalent to smart
sensors.

16. Applications
 Accelerometer
 Optical sensor
 Infrared detector array
 Integrated multi-sensor
 Geological mapping

17. Advantages
 Minimum Interconnecting Cables.
 High Reliability.
 High Performance.
 Easy to Use and Maintain.
 Scalable-Flexible System.
 Small Rugged Packaging.
 Small in size.

18. Disadvantages
 The smart sensor consists of both actuators & sensors,
so it is more complex than other simple sensors.
 The complexity is much higher in the wired smart
sensors, as a consequence the costs are also higher.
 Sensor calibration has to be managed by an external
processor.
 Predefined embedded functions have to be given
during the design of the smart sensor.