• Sensors are devices that responds to a physical
stimulus heat, light, sound, pressure, magnetism,
motion, etc , and convert that into an electrical signal.
They perform an input function.
• Devices which perform an output function are
generally called Actuators and are used to control
some external device, for example movement.
• Both sensors and actuators are collectively known as
Transducers. Transducers are devices used to
convert energy of one kind into energy of another
A smart sensor is an analog/digital transducer combined
with a processing unit and a communication interface. It
consists of transduction element, signal conditioning
electronic and controller/processor that support some
intelligence in a single package.
This integrated sensors which has electronics and the
transduction element together on one silicon chip, this
system can be called as system-on-chip (SoC).The main
aim of integrating the electronics and the sensor is to
make an intelligent sensor, which can be called as smart
sensor. Smart sensors then have the ability to make
Smart sensors / Intelligent sensor
are sensors with integrated
electronics that can perform one
or more of the following
1. Data Conversion
2. Bidirectional communication
3. Take decisions
4. Perform logical operations
TYPES OF SMART SENSORS
SMART SENSOR HYBRID
Three different types of configurations
are shown in which all the components
are placed on a chip. This is called
standardization. In the first hybrid
system, a sensor is connected with ADC
and bus interface with the help of
universal sensor interface. The second
configuration shows the connection of
sensor analog system with the digital
circuit and bus interface. In the third
configuration, sensor is combined with
the interface circuit already to provide
duty cycle and bit stream as shown in
INTEGRATED SMART SENSORS
If we integrate all functions from sensor to bus interface in one chip, we get an
integrated smart sensor as shown in figure below.
SMART SENSOR NETWORK
A sensor network is a collection of sensors interconnected with each other by a
communication network. A sensor network is made up of individual
multifunctional sensor nodes. It has much significance like sensing accuracy, area
coverage, connectivity, minimal human interaction.
Figure below shows the elements of a single network node.
2. SMART SENSOR ARCHITECTURE
The basic architectural components of smart sensor are listed
Sample and hold,
Analog to digital converter (ADC),
Offset and temperature
Digital to analog converter (DAC),
Five main parts of sensor node are:
The central unit: It is in the
form of microprocessor which
manages the tasks.
Battery: Is the source of
A Transceiver: Interacts with
the environment and collects
Memory: Used as storage
media for storing data or
Communication module: It
includes transceivers and
forwards queries and data to
and from central module. 
The signals recorded by many sensors are typically low in
amplitude, Integration of interface electronics and signal
processing circuitry at the sensor site (monolithic or hybrid)
serves a number of functions, including signal amplification,
impedance transformation, signal filtering and buffering, and
CMOS amplifiers are perhaps the most suitable since they
provide high gain and high input impedance through a
relatively simple and compact circuit and are readily
compatible with integration of high-density digital circuitry on
the same chip.
In addition to signal amplification, impedance transformation
and signal filtering are also required.
Digital Processing and Manipulation
The main circuit block required before digital control and
manipulation of sensor data can take place is the analog-digital
Once the sensor data is digitized, a variety of signal
processing schemes can be used to correct for a number
of errors and shortcomings. These include offset
cancellation, auto-calibration, self-testing, fault detection
and correction and linearity correction.
Auto-calibration is a very desirable function for smart
sensors. Most sensors should be adjusted for changes in
gain and offset.
Reliability and accuracy.
Communication and Bus Interaction
• A smart sensor should be capable of interacting with a
higher level controller that manages the overall system.
• Efforts are currently underway to develop such a standard
bus for sensor applications that is uniquely designed to
optimize functionality, speed and overall cost.
• A variety of information can be exchanged between the
sensor and the controller over the bus, including calibration
and compensation data, addresses and personality
information, measured data, and programming data initiated
by the controller, the communication interface should have
the ability to receive and transmit information over the bus
at a fairly high speed it should be noted that many sensor
signals have limited bandwidth and even in the case of a
multi-sensor system, the bus data rate may be sufficient to
accommodate all sensors 
Sensor is made with the same technology as
integrated circuit. A smart sensor utilizes the
transduction properties of one class of materials and
electronic properties of silicon (GaAs)
One problem with silicon is that its sensitivities to
strain, light and magnetic field show a large cross-sensitivity
to temperature. When it is not possible to
have silicon with proper effects, it is possible to
deposit layers of materials with desired sensitivity on
the top of a silicon substrate.
• Solid- State integrated
sensors are basically
composed of four elements
namely, custom films for
interface circuitry and
microcomputer based signal
Mainly, three techniques
surface micromachining and
wafer bonding process are
used for fabrication of smart
• Fig showing the fabrication
of a pressure sensor
4. ADVANTAGES AND DISADVANTAGES
The smart sensor takes over the conditioning and control of the
sensor signal, reducing the load on the central control system,
allowing faster system operation.
Direct digital control provides high accuracy, not achievable
with analog control systems and central processing.
The cost of smart sensor systems is presently higher than that
of conventional systems, but when the cost of maintenance,
ease of programming, ease of adding new sensors is taken into
account, the long- term cost of smart sensor systems is less.
Individual controllers can monitor and control more than one
If upgrading to smart sensors, care has to be taken when
mixing old devices with new sensors, since they may not be
If a bus wire fails, the total system is down, which is not the
case with discrete wiring. However, with discrete wiring, if
one sensor connection fails, it may be necessary to shut the
system down. The problem of bus wire failure can be
alleviated by the use of a redundant backup bus.
In industries machines and equipments are monitored and
controlled for pressure, temperature , humidity level and also
Communications between engine, transmission, suspension, braking
and other controls has long been anticipated.
FINGER PRINT RECOGNISITION
A fingerprint sensor is an electronic device used to capture a digital
image of the fingerprint pattern. The captured image is called a live
scan. This live scan is digitally processed to create a biometric template
(a collection of extracted features) which is stored and used for
The sensor uses incident light or backlight to detect
the contours of an object and compares them with the
contours of one or several models in a reference
A smart card known as a Wireless Identity Module, is
similar to the Subscriber Identity Module (SIM) used
on existing GSM cellular phones. The card
guarantees 100-percent security for e-commerce
transactions by providing authentication of the parties
involved, by means of encryption and digital
These days the trend in toys is to make them as life-like as
possible which move or change directions after sensing objects
Smart dust is a hypothetical wireless network of tiny micro-electro-
mechanical (MEMS) sensors, robots, or devices, which
can detect (for example) light, temperature, or vibration. The
devices will eventually be the size of a grain of sand, or even a
dust particle, with each mote having self-contained sensing,
computation, communication and power.
A number of smart sensors for biomedical applications have
also been developed by using chip technology .e.g. biochips
Cyto-sensor micro-physio-meter: biological applications of
MEMS AND PROCESS CONTROL
MEMS (Micro-Electro-Mechanical Systems) is a class of
systems that are physically small. These systems have both
electrical and mechanical components. MEMS originally used
modified integrated circuit (computer chip) fabrication
techniques and materials to create these very small mechanical
Smart cameras that can operate sophisticated software
analytics onboard the camera itself, and then report alarms
remotely using IP networking facilities. It has ability to
perform object detection, crowd pattern analysis, secure zone
intrusion detection, and so on boost the efficiency and
accuracy of a human operator who is likely monitoring
multiple banks of displays.
Smart sensor equipments helps in monitoring a wide variety of
parameters like EMI, fatigue loading, thermal cycling,
vibration and shock levels, acoustic emissions and corrosive
Automization can’t be imagined without the smart sensors.
These sensors are potentially cheaper, offer higher
performance and reliability, and are much smaller in size than
their discrete counterparts. They have also been employed in
applications including transportation and health care and in
large part have fulfilled their promise.
Sensor signals can be amplified and properly processed, are
multiplexed and are buffered ready to be received by micro-processor
on these signals and offer a standard data stream to
the user thus making the entire sensing module behave like a
system periphery rather than a passive component.
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[Retrieved on 11-11-2014]