S1-3_microsensors-ppt

7/28/2019 S1-3_microsensors-ppt

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MICROSENSORS

By:KARTHIK SUBRAY BHAT

CWID : 11472940.


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OVERVIEW

Introduction to and classification of Microsensors

Need for Microsensors

Trends in Microsensors

Types of Microsensors; Sensing principles, functionality and features


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INTRODUCTION

A microsensor is an extremely small device capable of picking up and relayingenvironmental information. Microsensors can be termed as transducers, as they

convert one form of energy into another. Microsensors basically converts measured

mechanical signal (non-electrical physical or chemical quantity) into an electrical

signal. These electrical signals are passed on to a processor and processor then

converts these signals into meaningful information for variety of applications.

A microsensor can be as small as few nanometres to few millimetres in size. They

can plug into a sensor array to collect a variety of data, and may interface

wirelessly with processors for ease of operation.

The way microsensors are designed must include a way of collecting the desired

information, which can depend on how the device will be used. Some microsensorsallow realtime reading abilities, which can be useful for activities like monitoring

cells in culture. Others store data which must be downloaded when researchers

want to interact with it.


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Classification of Microsensors


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Why do we need Microsensors?

low manufacturing costsbecause of mass production and materials required are less

wider exploitation of IC technology

wider applicability to sensor arrayslower weight

The need for microsensors is not only because of the advantages that are listed above

that can be exploited, but also because of the various fields it finds applications.

Listed below are some examples of applications of Microsensors.

Examples of Automotive Applications:


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MedicalApplications


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General requirements for a sensor:

The following are some of the requirements of a sensor:

It must be less sensitive to secondary inputsif not the output readings might be

inaccurate.

It must be stable for a long term.

Low pressure and temperature hysteresis

Small size and low cost

Resistance to corrosive ambient

Biocompatibility with the body

Trends in Microsensors:

The basic trends that we can see in Microsensors are as follows:

Miniaturization: The trend follows such that the feature size of the each component

is being made smaller and smaller. This is because of the fact that with smaller sizes

we can have high volume and thus lower cost.

Integration: Sensors are being integrated with signal processing circuits for various

functions one such being linearization of the output. Sensors can also have a built-inactuator for self test, automatic calibration, change of sensitivity etc..

Array of Sensors: Nowadays it is so that we are not having a single sensors but an

array of sensors. This is done so that we can get more reliable outputs and also larger

output signals.


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Chemical sensor is used to detect the presence of or

concentration of a chemical substance. These sensors find

applications in Medical Diagnostics, Nutritional Sciences,

Environmental Protection and Automobile Industry.

A sensitive layer sensitive to particular chemicals is in contact

with the substance. Chemical reaction takes place on thesensitive layer. Due to the reaction physical, optical, acoustic

or dielectric properties are changed. Transducers transform

these changes into electrical signals.

Optical sensors are cheap and can be sterilized easily. It can

handle small samples and are highly sensitive. A coupling

grid detector is used here. The substance to be analysed is in

direct contact with the waveguide. The index of refraction

varies depending on the concentration of the substance. In

other words, the amount of light striking the detector

depends on the concentration.

A biosensor is an analytical device for the detection of an

analyte that combines a biological component with a

physicochemical detector component. Sensitive layer is

made of biologically sensitive components such asenzymes or anti-bodies. Molecules of the bioelement and

the molecules of the substance interact to produce

changes in physical or chemical parameter. These

parameter changes are converted into electrical signals.

Signals represent concentration to be measured.


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Pressure sensors are used measure the pressure of gases or liquids. They can be broadly

classified into two: Absolute and Relative pressure sensors.

Piezoresistive pressure sensor: Piezoresistors

are integrated on the membrane. Pressure

causes stress on the membrane which causes

the change in the resistance. This resistance

change is calculated using a Wheat-stone

bridge. The change in resistance is calculated

into pressure.


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Piezoresistive pressure sensors

Left: Sensonors absolute pressure sensor.

Right: Motorolas MAP sensor

Capacitive membrane pressure sensor:

Membrane changes when pressure is applied. Due to this the distance between the

electrodes changes and so does capacitance. They dont have hysteresis and have better

long-term stability and higher sensitivity but higher production costs.

Tohokus pressure sensor


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Position and Speed Microsensors: Accelerometers and gyroscopes are used to calculate

acceleration and position respectively. These sensors find applications in Automobiles, Robots

and Medical Instruments. Piezoresistive accelerometers and capacitive accelerometers are the

accelerometer sensors commonly used.

The advantages of piezoresistive accelerometers are: they have simpler structures, simpler

fabrication process, and simpler read-out circuitry. And the disadvantages are: Larger

temperature sensitivity, lower mechanical sensitivity, high power consumption. The

advantages of capacitive accelerometers are: high sensitivity, good DC performance and noise

performance, low drift, low temperature sensitivity, low power consumption. The

disadvantages are: susceptible to electromagnetic interference, non-linear output.

Left: Piezoresistive accelerometer: In

the figure the top sensor is called

SA50 and has two axes crash sensors.

The bottom sensor is called SAC60

and has 1-axis side crash sensor.

Right : Capacitive accelerometer:

Fords accelerometer


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Gyrosopes: It consists of two high performance MEMS devices integrated in one: A self-tuned

resonator in the drive axis and a micro-accelerometer in the sensing axis. They are very sensitive to

all potential manufacturing variations, packaging, linear acceleration, temperature, etc. Low-noise

read-out, signal processing and control electronics are required. Tuning fork gyroscopes and disk

gyroscopes are the two types of gyroscopes.

Top left:Drapers double-gimbal gyroscope

TopRight:Comb-drive gyroscope

Left:Silicon MicroRing gyroscope


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Acknowledgement

I thank Dr. Weili Zhang for giving me an opportunity to select Microsensors as

my topic and write a term paper and do a presentation on the same. I learnt a lot

about microsensors and their applications while doing this paper.


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References:

Microsensors- documentation by Daniel Lapadatu, SensoNor Technologies.http://mspde.usc.edu/inspiring/resource/sensor/Microsensors.pdf

http://en.wikipedia.org/wiki/Wheel_speed_sensor

http://en.wikipedia.org/wiki/Biosensor

http://www.intechopen.com/books/microsensors

http://noc.ac.uk/science-technology/research-groups/ote/instruments-sensors/biological-

microsensors
http://mspde.usc.edu/inspiring/resource/sensor/Microsensors.pdfhttp://en.wikipedia.org/wiki/Wheel_speed_sensorhttp://en.wikipedia.org/wiki/Biosensorhttp://www.intechopen.com/books/microsensorshttp://noc.ac.uk/science-technology/research-groups/ote/instruments-sensors/biological-microsensorshttp://noc.ac.uk/science-technology/research-groups/ote/instruments-sensors/biological-microsensorshttp://noc.ac.uk/science-technology/research-groups/ote/instruments-sensors/biological-microsensorshttp://noc.ac.uk/science-technology/research-groups/ote/instruments-sensors/biological-microsensorshttp://noc.ac.uk/science-technology/research-groups/ote/instruments-sensors/biological-microsensorshttp://noc.ac.uk/science-technology/research-groups/ote/instruments-sensors/biological-microsensorshttp://noc.ac.uk/science-technology/research-groups/ote/instruments-sensors/biological-microsensorshttp://noc.ac.uk/science-technology/research-groups/ote/instruments-sensors/biological-microsensorshttp://noc.ac.uk/science-technology/research-groups/ote/instruments-sensors/biological-microsensorshttp://noc.ac.uk/science-technology/research-groups/ote/instruments-sensors/biological-microsensorshttp://noc.ac.uk/science-technology/research-groups/ote/instruments-sensors/biological-microsensorshttp://noc.ac.uk/science-technology/research-groups/ote/instruments-sensors/biological-microsensorshttp://noc.ac.uk/science-technology/research-groups/ote/instruments-sensors/biological-microsensorshttp://noc.ac.uk/science-technology/research-groups/ote/instruments-sensors/biological-microsensorshttp://noc.ac.uk/science-technology/research-groups/ote/instruments-sensors/biological-microsensorshttp://noc.ac.uk/science-technology/research-groups/ote/instruments-sensors/biological-microsensorshttp://noc.ac.uk/science-technology/research-groups/ote/instruments-sensors/biological-microsensorshttp://www.intechopen.com/books/microsensorshttp://www.intechopen.com/books/microsensorshttp://www.intechopen.com/books/microsensorshttp://www.intechopen.com/books/microsensorshttp://www.intechopen.com/books/microsensorshttp://www.intechopen.com/books/microsensorshttp://www.intechopen.com/books/microsensorshttp://en.wikipedia.org/wiki/Biosensorhttp://en.wikipedia.org/wiki/Biosensorhttp://en.wikipedia.org/wiki/Biosensorhttp://en.wikipedia.org/wiki/Biosensorhttp://en.wikipedia.org/wiki/Biosensorhttp://en.wikipedia.org/wiki/Biosensorhttp://en.wikipedia.org/wiki/Biosensorhttp://en.wikipedia.org/wiki/Wheel_speed_sensorhttp://en.wikipedia.org/wiki/Wheel_speed_sensorhttp://en.wikipedia.org/wiki/Wheel_speed_sensorhttp://en.wikipedia.org/wiki/Wheel_speed_sensorhttp://en.wikipedia.org/wiki/Wheel_speed_sensorhttp://en.wikipedia.org/wiki/Wheel_speed_sensorhttp://en.wikipedia.org/wiki/Wheel_speed_sensorhttp://mspde.usc.edu/inspiring/resource/sensor/Microsensors.pdfhttp://mspde.usc.edu/inspiring/resource/sensor/Microsensors.pdfhttp://mspde.usc.edu/inspiring/resource/sensor/Microsensors.pdfhttp://mspde.usc.edu/inspiring/resource/sensor/Microsensors.pdfhttp://mspde.usc.edu/inspiring/resource/sensor/Microsensors.pdfhttp://mspde.usc.edu/inspiring/resource/sensor/Microsensors.pdfhttp://mspde.usc.edu/inspiring/resource/sensor/Microsensors.pdfhttp://mspde.usc.edu/inspiring/resource/sensor/Microsensors.pdfhttp://mspde.usc.edu/inspiring/resource/sensor/Microsensors.pdf


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THANK YOU

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