Smart sensors

                                                   

ABSTRACT 

Smart sensors represent the next evolutionary tools for studying the environment. The smart environment relies first and foremost on sensory data from the real world. Sensory data comes from smart sensors of different modalities in distributed locations. Smart sensor systems are capable of prediction, interpretation, communication and intelligent interaction with the environment & hence will leverage new fault management of devices and control for distributed resources. Tremendous advances in digital signal processing and laser capabilities in recent years have enabled many new sensor developments, one of these being smart sensors. Fundamental research has already been carried out to develop smart sensors to monitor and control robotics, mobile vehicles, cooperative autonomous systems, mechatronics and bioengineering systems. Emerging sensors and instrumentation technology can be exploited for enhanced research and operational capabilities. Such smart information technology manifests the potential for varied applications. It is envisioned that concepts of smart sensors and information technology can be transferred and applied to numerous system. The implementation of large networks of interconnected smart sensors can monitor and control our world. Better understanding of smart sensors perform satisfactorily in real-world conditions and can help improve efficiency and reliability. A sensor network consisting of a large number of smart sensors, enabling the collection, processing analysis and dissemination of valuable information gathered in a variety of environments is being implemented quickly . 

II LIST OF FIGURES Fig No. Title Page No. i General Architecture of Smart Senosr 8 Ii Thermistor 11 Iii Infrared Sensor 11 Iv Capacitive proximity sensor 12 V Air pressure sensor 13 Vi Water pressure sensor 13 Vii Gas sensor 13 Viii Alcohol sensor 13 Ix Photoelectric smoke sensor 14 X Ionization smoke sensor 14 Xi linear hall-effect accelerometer 15 Xii Piezoelectric accelerometer 15 Xiii Liquid level sensor 15 Xiv Float type level sensor 15 Xv Ultrasonic sensor 16 Xvi passive infrared sensor 16 Xvii Digital gyroscope 17 Xvii i Optical gyroscope 17 Xix Ph sensor 17 Xx Water conductivity sensor 17 1 

1.INTRODUCTION

 The advent of integrated circuits, which became possible because of the tremendous progress in semiconductor technology, resulted in the low cost microprocessor. Thus if it is possible to design a low cost sensor which is silicon based then the overall cost of the control system can be reduced .We can have integrated sensors which has electronics and the transduction element together on one silicon chip. This complete system can be called as system-on-chip .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 some decision. Physically a smart sensor consists of transduction element, signal conditioning electronic and controller/processor that support some intelligence in a single package. In this report the physical phenomena of conversion to electrical output using silicon sensors, characteristics of smart sensors. A general Smart sensors are an extension of traditional sensors to those with advanced learning and adaptation capabilities. The system must also be re-configurable and perform the necessary data interpretation, fusion of data from multiple sensors and the validation of local and remotely collected data.These sensors therefore contain embedded processing functionality that provides the computational resources to perform complex sensing and actuating tasks along with high level applications. The functions of an smart sensor system can be described in terms of compensation, information processing, communications and integration. The combination of these respective elements allow for the development of these sensors that can operate in a multi-modal fashion as well conducting active autonomous sensing. Compensation is the ability of the system to detect and respond to changes in the network environment through self-diagnostic routines, self-calibration and adaptation. A smart sensor must be able to evaluate the validity of collected data, compare it with that obtained by other sensors and confirm the accuracy Information processing encompasses the data related processing that aims to enhance and interpret the collected data and maximize the efficiency of the system, through signal conditioning, data reduction, event detection and decision making. Communications component of sensor systems incorporates the standardized network protocol which serves to links the distributed sensors in a coherent manner, enabling efficient communications and fault tolerance. Integration in smart sensors involves the coupling of sensing and computation at the chip level. This can be implemented using micro electro-mechanical systems (MEMS), nano-technology and bio-technology. Validation of sensors is required to avoid the potential disastrous effects of the propagation of erroneous data. The incorporation of data validation into smart sensors increases the overall reliability of the system 2

 2. DEFINITION Smart sensors are sensors with integrated electronics that can perform one or more of the following function logic functions, two-way communication, make decisions. 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 on it.

 3.SMART SENSOR NETWORKS : Wireless sensor networks are potentially one of the most important technologies of this century. A sensor network is an array of sensors of diverse type interconnected by a communications network. Sensor data is shared between the sensors and used as input to a distributed estimation system which aims to extract as much relevant information from the available sensor data. The fundamental objectives for sensor networks are reliability, accuracy, flexibility, cost effectiveness and ease of deployment. A sensor network is made up of individual multifunctional sensor nodes. The sensor node itself may be composed of various elements such as various multi-mode sensing hardware (acoustic, seismic, infrared, magnetic, chemical, imagers, microradars), embedded processor, memory, power-supply, communications device (wireless and/or wired) and location determination capabilities . A sensor network can be described by services, data and physical layer respectively. 

3.1 SIGNIFICANCE OF SENSOR NETWORK:  Sensing accuracy: The utilization of a larger number and variety of sensor nodes provides potential for greater accuracy in the information gathered as compared to that obtained from a single sensor.  Area coverage: A distributed wireless network will enable the sensor network to span a greater geographical area without adverse impact on the overall network cost.  Fault tolerance: Device redundancy and consequently information redundancy can be utilized to ensure a level of fault tolerance in individual sensors.  Connectivity: Multiple sensor networks may be connected through sink nodes, along with existing wired networks (eg. Internet).  Minimal human interaction: The potential for self-organizing and self maintaining networks along with highly adaptive network topology significantly reduce the need for further human interaction with a network other than the receipt of information. 3  Operability in harsh environments: Robust sensor design, integrated with high levels of fault tolerance and network reliability enable the deployment ofsensor.

 4.USEFULNESS OF SILICON TECHNOLOGY IN SMART SENSOR There are very convincing advantages of using silicon technology in the construction of smart sensor. All integrated circuits employ silicon technology. A smart sensor is made with the same technology as integrated circuits. A smart sensor utilizes the transduction properties of one class of materials and electronic properties of silicon (GaAs). A transduction element either includes thin metal films, zinc oxide and polymeric films. Integrating electronics circuits on the sensor chip makes it possible to have single chip solution. Integrated sensors provide significant advantages in terms of overall size and the ability to use small signals from the transduction element. The IC industry will get involved in smart sensor if a very large market can be captured and the production of smart sensor does not require non-standard processing steps. 

4.1 Signal conversion effects We know that silicon shows a suitable physical signal conversion effect. Many of the physical effects of silicon can be used in making sensors. Based on these effects, different types of sensors can be constructed which can be used for measuring different physical and chemical measurand. Table1 below shows how different non electrical signal in which we can classify different measurand and Table 2 shows the physical effects for sensors in silicon. 4 One problem with silicon is that its sensitivities to strain, light and magnetic field show a large crosssensitivity to temperature. When it is not possible to have silicon with proper effect, it is possible to deposit layers of materials with desired sensitivity on the top of a silicon substrate. Thus we can have a magnetic field sensor by depositing Ni-Fe layer on the top of a silicon substrate.

 4.2 Different Silicon Sensors Employing Above Effects Radiant Signal Domain Silicon can be used to construct a sensor for sensing wide range of radiant signal from gamma rays to infrared. Silicon can be used for the fabrication of photoconductors, photodiode, and phototransistor or to detect nuclear radiation. Mechanical Signal Domain Silicon can be used for measuring force and pressure because of the piezo resistance effect. This effect is large because the average mobility of electrons and holes in silicon is strongly affected by the application of strain. Silicon can also be used for the measurement of air or gas velocities. If we slightly heat a silicon structure having two temperature measuring devices, and is brought into airflow then the By photoelectric principle one can find angular position by employing resulting a temperature difference is proportional to the square root of the flow velocity. Combining a piezo resistor, diffused in a cantilevered beam or a piezoelectric layer with silicon can make a miniature accelerometer. two photodiodes (i.e. one for X co-ordinate and other for Y) Thermal Signal Domain We know that all electron devices in silicon show temperature dependence, this property of silicon can be used for the measurement of temperature. This can be achieved by using two bipolar transistors with a constant ratio of emitter current. Another way of measuring temperature is to integrate thermocouples consisting of evaporated aluminium films and diffused p-type and n-type layers. This is possible because Seebeck in silicon is 5 very large. Magnetic Signal Domain Silicon is a non –magnetic material but it can be used for the construction of Hall plates and transistor structures that are sensitive to magnetic fields. These sensors are constructed by depositing a thin magnetic Ni-Fe film on top of silicon chip that also contains electronic circuits. Chemical Signal Domain The demand for the better process control for bio-medical, automotive and environmental applications has encouraged many laboratories to undertake silicon chemical sensor. The ion-sensitive FET (ISFET) is best suitable for such application. When an ISFET with properly chosen ion-sensitive gate insulators is immersed in an electrolyte,the change of the drain current is a measure of the concentration of the ions or the pH.Chemical sensors can be used as humidity sensor or gas sensor. 

4.3 Suitable Silicon Processing Circuit Using Silicon The silicon sensor can produce output as voltage, current, resistance or capacitance, output format can be analog or digital. Suitable signal conditioning circuits along with processor can easily designed using silicon technology. 

5. Importance and Adoption of Smart Sensor The presence of controller/processor in smart sensor has led to corrections for different undesirable sensor characteristics which include input offset and span variation, non-linearity and cross-sensitivity. As these are carried in software, no additional hardware is required and thus calibration becomes an electronic process. Thus it is possible to calibrate the batches of sensor during production without the need to remove the sensor from its current environment or test fixture. 5.1 Cost improvement In case of smart sensor inside hardware is more complex in the sensor on the other hand it is simpler outside the sensor. Thus the cost of the sensor is in its setup, which can be reduced by reducing the effort of setup, and by removing repetitive testing. 6

 5.2 Reduced cost of bulk cables and connectors Use of smart sensor has significantly reduced the cost of bulk cables and connectors needed to connect different blocks (i.e. electronic circuits). 5.3 Remote Diagnostics Due to the existence of the processor with in the package, it is possible to have digital communication via a standard bus and a built in self-test (BIST). This is very helpful in production test of integrated circuits. This diagnostic can be a set of rules based program running in the sensor. 5.4 Enhancement of application Smart sensor also enhances the following applications:  Self calibration  Computation  Communication  Multisensing Self calibration: Self-calibration means adjusting some parameter of sensor during fabrication, this can be either gain or offset or both. Self-calibration is to adjust the deviation of the output of sensor from the desired value when the input is at minimum or it can be an initial adjustment of gain. Calibration is needed because their adjustments usually change with time that needs the device to be removed and recalibrated. the manufacturer over-designs, which ensure that device, will operate within specification during its service life. These problems are solved by smart sensor as it has built in microprocessor that has the correction functions in its memory Computation: Computation also allows one to obtain the average, variance and standard deviation for the set of measurements. This can easily be done using smart sensor. Computational ability allows to compensate for the environmental changes such as temperature and also to correct for changes in offset and gain. Communication: Communication is the means of exchanging or conveying information, which can be easily accomplished by smart sensor. This is very helpful as sensor can broadcast information about its own status and measurement uncertainty. 7 Multisensing Some smart sensor also has ability to measure more than one physical or chemical variable simultaneously. A single smart sensor can measure pressure, temperature, humidity gas flow, and infrared, chemical reaction surface acoustic vapor etc. 5.5 System Reliability System reliability is significantly improved due to the utilization of smart sensors. One is due to the reduction in system wiring and second is the ability of the sensor to diagnose its own faults and their effect. 5.6 Better Signal to Noise Ratio The electrical output of most of the sensors is very weak and if this transmitted through long wires at lot of noise may get coupled. But by employing smart sensor this problem can be avoided. 

5.7 Improvement in characteristics Non-linearity: Many of the sensors show some non-linearity, by using on-chip feedback systems or look up tables we can improve linearity. Cross-sensitivity: Most of the sensors show an undesirable sensitivity to strain and temperature. Incorporating relevant sensing elements and circuits on the same chip can reduce the cross-sensitivity. Offset: Offset adjustment requires expensive trimming procedures and even this offsets tend to drift. This is very well reduced by sensitivity reduction method. Parameter drift and component values: These are functions of time. This can be solved by automatic calibration. 8 6. GENERAL ARCHITECTURE OF SMART SENSOR: One can easily propose a general architecture of smart sensor from its definition, functions. From the definition of smart sensor it seems that it is similar to a data acquisition system, the only difference being the presence of complete system on a single silicon chip. In addition to this it has on–chip offset and temperature compensation. A general architecture of smart sensor consists of following important components: Sensing element/transduction element, Amplifier, Sample and hold, Analog multiplexer, Analog to digital converter (ADC), Offset and temperature compensation, Digital to analog converter (DAC), Memory, Serial communication and Processor The generalized architecture of smart sensor is shown below: Fig I 9

 6.1 Description of Smart Sensor Architecture Architecture of smart sensor is shown. In the architecture shown A1, A2…An and S/H1, S/H2…S/Hn are the amplifiers and sample and hold circuit corresponding to different sensing element respectively. So as to get a digital form of an analog signal the analog signal is periodically sampled (its instantaneous value is acquired by circuit), and that constant value is held and is converted into a digital words. Any type of ADC must contain or proceeded by, a circuit that holds the voltage at the input to the ADC converter constant during the entire conversion time. Conversion times vary widely, from nanoseconds (for flash ADCs) to microseconds (successive approximation ADC) to hundreds of microseconds (for dual slope integrator AD Cs). ADC starts conversion when it receives start of conversion signal (SOC) from the processor and after conversion is over it gives end of conversion signal to the processor. Outputs of all the sample and hold circuits are multiplexed together so that we can use a single ADC, which will reduce the cost of the chip. Offset compensation and correction comprises of an ADC for measuring a reference voltage and other for the zero. Dedicating two channels of the multiplexer and using only one ADC for whole system can avoid the addition of ADC for this. This is helpful in offset correction and zero compensation of gain due to temperature drifts of acquisition chain. In addition to this smart sensor also include internal memory so that we can store the data and program required. 7. BLOCK LEVEL DESIGN CONSIDERATIONS FOR SMART SENSOR Design choice of smart sensor depends on the specific application for which the sensor is required and also related to specific industry. Normally a smart sensor will utilize inputs form one or more sensor elements either to generate an output signal or to generate a correction signals which are applied to the primary output. This includes design of circuitry to take output of raw sensor elements and generate compensated and linearized sensor output.

 7.1 Functions within electronics: The smart sensor contains some or all of the following functions Sensor Excitation: Many a times it is required to alter the sensor excitation over the operating range of a sensor. An example of this is a silicon wheat stone bridge, where the drive voltage is increased with increasing temperature. This is done to compensate for the reduction in sensitivity of the piezoresistors with increase in temperature. A drive stage with temperature dependence can be used which is control by a microprocessor. This will also reduce the calibration time. 10 Analogue Input: Multiplexing of inputs can be done to avoid duplication of circuit. In multiplexing inputs of same type and range are switched to a common front end. The outputs of sensors are normalized before they are switched and a variable gain stage is included after the multiplexer.In addition to this an offset adjustment is also included in the common front end. The variable gain stage also offers an additional advantage where the input signals are to be sampled by analog to digital converter (ADC) with fixed reference points. Under such situation gain can be increased at the lower end to increase the sensitivity. Data Conversion: In case of smart sensor most of the signal processing is done in digital form. This is possible only when we have an ADC along with an anti-aliasing filter. This is because most of the sensor output is in the analog form. Choice of ADC depends on the resolution, bandwidth and complexity of anti-aliasing filter. Digital data bus interface: The controller embedded in the smart sensor supports communications by digital data bus. The advantages of this are: Wiring is reduced considerably Automatic calibration at production can be simplified. Monitoring and diagnostic functions: In many applications self-test is required. This self-test includes connectivity checking and long-term offset correction. Control processor: To provide greater flexibility and reduced complexity, a control processor can be used. Control processor can do digital filtering. Another important point is software development. Processor must allow writing codes in higher language as it reduces the development time. 

7.2 Level of integration: Though it is possible to integrate smart sensor on a single piece of silicon it is unattractive due to cost and performance. Analog processing, digital logic and nonvolatile memory (NVRAM), can all be done on same piece of silicon. But compromise 11 must be made that limit the performance of at least one of these functions.

 8. SUMMARY OF DIFFERENT SMART SENSORS: Some of the smart sensors developed at different research institutes are as follow: o Temperature Sensors o Proximity Sensor o Pressure Sensor o Gas & Smoke Sensor o Accelerometer Sensors o Level Sensors o Image Sensors o Motion Detection Sensors o Optical Sensors o Gyroscope Sensors Temperature Sensors: A temperature sensor is an electronic device that measures the temperature of its environment and converts the input data into electronic data to record, monitor, or signal temperature changes. fig ii :thermistor fig iii: infraredsensor There are many different types of temperature sensors. Some temperature sensors require direct contact with the physical object that is being monitored (contact temperature sensors), while others indirectly measure the temperature of an object (noncontact temperature sensors). 

12 Temperature sensors are used in automobiles, medical devices, computers, cooking appliances, and other types of machinery. Proximity Sensors: A proximity sensor is a sensor able to detect the presence of nearby objects without any physical contact. A proximity sensor often emits an electromagnetic field or a beam of electromagnetic radiation (infrared, for instance), and looks for changes in the field or return signal. The object being sensed is often referred to as the proximity sensor's target. Different proximity sensor targets demand different sensors. For example, a capacitive proximity sensor or photoelectric sensor might be suitable for a plastic target; an inductive proximity sensor always requires a metal target. fig iv: capacitive proximity sensor Proximity sensors are also used in machine vibration monitoring to measure the variation in distance between a shaft and its support bearing. This is common in large steam turbines, compressors, and motors that use sleeve-type bearings. Pressure Sensors: A pressure sensor is a device for pressure measurement of gases or liquids. Pressure is an expression of the force required to stop a fluid from expanding, and is usually stated in terms of force per unit area. A pressure sensor usually acts as a transducer; it generates a signal as a function of the pressure imposed. For the purposes of this article, such a signal is electrical. Pressure sensors can vary drastically in technology, design, performance, application suitability and cost. A conservative estimate would be that there may be over 50 technologies and at least 300 companies making pressure sensors worldwide. There is also a category of pressure sensors that are designed to measure in a dynamic mode for capturing very high speed changes in pressure. Example applications for this type of sensor would be in the measuring of combustion pressure in an engine cylinder or in a gas turbine. These sensors are commonly manufactured out of piezoelectric materials such as quartz.

 13 fig v: (air pressure sensor) fig vi:(water pressure sensor) Pressure sensors are used for control and monitoring in thousands of everyday applications. Pressure sensors can also be used to indirectly measure other variables such as fluid/gas flow, speed, water level, and altitude. Pressure sensors can alternatively be called pressure transducers, pressure transmitters, pressure senders, pressure indicators, piezometers and manometers, among other names. Gas & Smoke Sensors: A gas sensor is a device which detects the presence or concentration of gases in the atmosphere. Based on the concentration of the gas the sensor produces a corresponding potential difference by changing the resistance of the material inside the sensor, which can be measured as output voltage. fig vii: (gas sensor) fig viii:(alcohol sensor)

 14 They are commonly used to detect toxic or explosive gasses and measure gas concentration. Gas sensors are employed in factories and manufacturing facilities to identify gas leaks, and to detect smoke and carbon monoxide in homes. Gas sensors vary widely in size (portable and fixed), range, and sensing ability. Smoke sensor: A smoke detector is an electronic fire-protection device that automatically senses the presence of smoke, as a key indication of fire, and sounds a warning to building occupants. Commercial and industrial smoke detectors issue a signal to a fire alarm control panel as part of a building's central fire alarm system. fig ix: (photoelectric smoke sensor) fig x:( ionization smoke sensor) A smoke sensor is a device fitted to smoke alarms. A smoke alarm is designed to detect the presence of smoke in a home to alert the occupants that a fire has broken out. A smoke alarm contains not only a smoke sensor but also a loud audible alarm (85 decibels on average) to alert people in the home. Accelerometer Sensors: An accelerometer is a device that measures the vibration, or acceleration of motion of a structure. The force caused by vibration or a change in motion (acceleration) causes the mass to "squeeze" the piezoelectric material which produces an electrical charge that is proportional to the force exerted upon it. The basic underlying working principle of an accelerometer is such as a dumped mass on a spring. When acceleration is experienced by this device, the mass gets displaced till the spring can easily move the mass, with the same rate equal to the acceleration it sensed.

 15 fig xi: (linear hall-effect accelerometer) fig xii:( piezoelectric accelerometer) Level Sensors: Level sensors detect the level of liquids and other fluids and fluidized solids, including slurries, granular materials, and powders that exhibit an upper free surface. Substances that flow become essentially horizontal in their containers (or other physical boundaries) because of gravity whereas most bulk solids pile at an angle of repose to a peak. The substance to be measured can be inside a container or can be in its natural form (e.g., a river or a lake). The level measurement can be either continuous or point values. Continuous level sensors measure level within a specified range and determine the exact amount of substance in a certain place, while point-level sensors only indicate whether the substance is above or below the sensing point. Generally the latter detect levels that are excessively high or low. fig xiii: (liquid level sensor ) fig xiv:( float type level sensor ) There are many physical and application variables that affect the selection of the optimal level monitoring method for industrial and commercial processes.[1] The selection criteria include the physical: phase (liquid, solid or slurry), temperature, pressure or vacuum, chemistry, dielectric constant of medium, density (specific gravity) of medium, agitation (action), acoustical or electrical noise, vibration, mechanical shock, tank or bin size and shape.

 16 Motion Detection Sensors: A motion detector is an electrical device that utilizes a sensor to detect nearby motion. Such a device is often integrated as a component of a system that automatically performs a task or alerts a user of motion in an area. They form a vital component of security, automated lighting control, home control, energy efficiency, and other useful systems. fig xv: (ultrasonic sensor) fig xvi:(passive infrared sensor ) A motion sensor uses one or multiple technologies to detect movement in an area. When a sensor detects motion, it sends a signal to your security system's control panel, which connects to your monitoring center. This alerts you and the monitoring center to a potential threat in your home. Gyroscope Sensor: A sensor or device which is used to measure the angular rate or angular velocity is known as Gyro sensors. The most important application is monitoring the orientation of an object. Gyroscopes based on other operating principles also exist, such as the microchippackaged MEMS gyroscopes found in electronic devices (sometimes called gyrometers), solid-state ring lasers, fibre optic gyroscopes, and the extremely sensitive quantum gyroscope. 

17 fig xvii: (digital gyroscope) fig xviii:( optical gyroscope) A Gyroscope can be understood as a device that is used to maintain a reference direction or provide stability in navigation, stabilizers, etc. Similarly, a gyroscope or a Gyro sensor is present in your smartphone to sense angular rotational velocity and acceleration. Water Quality Sensors: Water quality sensors are employed using two main approaches. They are either used to directly measure constituents of interest (chemical concentrations, solids, etc.) in the water, or to measure surrogates. Surrogates are chemical concentrations or solids that may indicate the presence of unanticipated contaminants in the water. Water quality sensors are used to detect the water quality and Ion monitoring primarily in water distribution systems. fig xix: (ph sensor) fig xx:( water conductivity sensor) 18 

9.A SMARTER WORLD:

 10. ADVANTAGES OF SMART SENSORS:  Accelerate processes and make them more accurate.  Collect process and asset data in real time.  Monitor processes and assets accurately, reliably, and continuously.  Increase productivity and reduce total cost of ownership.  Lower energy wastage.  High Reliability and Performance  Easy to Design, Use and Maintain  Can perform self-assessment and self-calibration 19 

11. DISADVANTAGES OF SMART SENSORS:  Narrow or limited temperature range. ...  Short or limited shelf life. ...  Cross-sensitivity of other gases. ...  The greater the exposure to the target gas, the shorter the life span.  Contains both actuators & sensors, so complexity is higher  Cost of Wired Smart Sensors are higher  Sensor Calibration has to be managed by an external processor  Predefined Embedded Functions have to be given during the design 

12. APPLICATIONS OF SMART SENSORS:  Industrial  Telecommunication  Biomedical applications  Defense Applications  Home Automation  Finger print recognition  Smart Dust

 12.1 What industries do benefit from smart sensors? Healthcare Sensors are vital in making healthcare management seamless. The various benefits include,  Monitoring hand hygiene compliance  Occupancy monitoring  Automate temperature and light settings  Human-centric lighting Warehouse and Manufacturing Smart sensors help manufacturing enterprises in improving employee well-being and profitable process workflows. The sensors generate relevant information of various kind like,  Historical data for decision making  Alerts and reminders on maintenance and repairs  Lighting automation to ensure active environments 

20  Improved space utilization Check how a California based leading environmental and industrial machinery manufacturer replaced their primitive in-house system to a smart facility. Hospitality Sensors designed for smart hotels enable cost savings, bring in revenue opportunities, and drastically improve guest experiences. For instance, thermostats and occupancy sensors allow smart energy-management that wisely utilizes energy, besides automating temperature controls and light settings. Let’s see some of the other benefits of sensors in the hospitality industry.  Automated guest interactions  Personalized experience delivery with guest data  Self-check-in/check-out and automated room entry  Push-notifications for room service Offices Sensor-based technology is changing the way employees interact and work in today’s offices. Smart-sensors are behind this transformation, ensuring improved productivity and performance. The list goes on!  Smart lighting for human-centricity  Smart HVAC systems for automated climate control  Intelligent conference room and occupancy data  Indoor way finding and smart-navigation Home Automation Today, there’s some sensor for every home function, or there will be one soon. Sensors are the backbone of home automation that directs smart devices on when to work and how to work.  Automated device activation  Mood lighting and temperature controls  Pre-set routine schedules  Theft and unauthorized access detection 21 

13.CONCLUSION In recent technologies, WSN has got the spotlight on it because of its unbeatable potential, significance and wide range of application areas. As wireless sensor technology has evolved, it has become possible to predict the future by using Smart environment which was not possible in the past. "Smart Sensors" is Wireless Sensor Network’s one step further. This paper is mainly focused on the study of smart sensors and their possible and existing usage in various fields The future work for Smart Sensors can include but not limited to Smart Grid for improved electric power efficiency, Smart Antenna for satisfying demands for drastic high data rates for certain users with high quality of service, Smart Highways for handling traffic and accident related issues. 22 14.REFERENCES: 1. Smartening the Environment using Wireless Sensor Networks in a Developing Country by Al-Sakib Khan Pathan, Choong Seon Hong, Hyung-Woo Lee. 2. Information circular 9496/2007, Department of Health and Human Services, USA 3. A Study on Saving Energy in Artificial Lighting by Making Smart Use of Wireless Sensor Networks and Actuators Alejandro FernándezMontes, Luis Gonzalez-Abril, Juan A. Ortega, and Francisco Velasco Morente, University of Seville 4. Smart Sensor Networks: Technologies and Applications for Green Growth December 2009, OECD 5. Wireless Sensor Networks, F. L. LEWIS, Associate Director for Research Head, Advanced Controls, Sensors, and MEMS Group Automation and Robotics Research Institute, The University of Texas at Arlington 6. Wireless Sensor Network Research Group.htm 7. Akyildiz, I. F., Su, W., Sankarasubramaniam, Y, and Cayirci, E., “Wireless Sensor Networks: A Survey”, Computer Networks, 38, 2002, pp. 393-422.