Sensors

The New Generation Technology

Group Members

Rashil MehtaYash BhanHarshit MathurAnkit YadavAnoop Kumar

Transducers

• Transducer– a device that converts a primary form of

energy into a corresponding signal with a different energy form.• Primary Energy Forms: mechanical, thermal, electromagnetic, optical,

chemical, etc.

– take form of a sensor or an actuator

• Sensor (e.g., thermometer)– a device that detects/measures a signal or stimulus– acquires information from the “real world”

• Actuator (e.g., heater)

– a device that generates a signal or stimulus

realworld

sensor

actuator

intelligentfeedbacksystem

Need of Sensors

• To be useful, systems must interact with their environment. To do this they use sensors and actuators.•Without the use of sensors, there would be no automation.• They are embedded in our bodies, automobiles, airplanes, cellular telephones, radios, chemical plants, industrial plants and countless other applications.

Detectable Phenomenon

Physical Principles

• Amperes' Law• A current carrying conductor in a magnetic field experiences a

force (e.g. galvanometer)

• Faraday’s Law of Induction• A coil resist a change in magnetic field by generating an

opposing voltage/current (e.g. transformer)

• Photoconductive Effect• When light strikes certain semiconductor materials, the

resistance of the material decreases (e.g. photoresistor)

Describing Sensor Performance

A good sensor obeys the following rules:•Is sensitive to the measured property only•Is insensitive to any other property likely to be encountered in its application•Does not influence the measured property

• Range•maximum and minimum values that can be measured

• Resolution or discrimination• smallest discernible change in the measured value

• Error• difference between the measured and actual values• random errors• systematic errors

• Accuracy, inaccuracy, uncertainty• accuracy is a measure of the maximum expected error

• Precision• a measure of the lack of random errors (scatter)

• Linearity• maximum deviation from a ‘straight-line’ response• normally expressed as a percentage of the full-scale value

• Sensitivity• a measure of the change produced at the output for a given

change in the quantity being measured

Choosing a Sensor

Types of Sensors

• Sensors in nature• Acoustic, sound, vibration• Chemical• Electric current, electric potential, magnetic, radio• Environment, weather, moisture, humidity• Flow, fluid velocity• Navigation instruments• Position, angle, displacement, distance, speed, acceleration• Optical, light, imaging, photon• Pressure• Force, density, level• Thermal, heat, temperature• Proximity, presence

Sensors in nature

All living organisms contain biological sensors with functions similar to those of the mechanical devices described. Most of these are specialized cells that are sensitive to:•Light, motion, temperature, magnetic fields, gravity, humidity, moisture, vibration, pressure, electrical fields, sound, and other physical aspects of the external environment•Physical aspects of the internal environment, such as stretch, motion of the organism, and position of appendages•Environmental molecules, including toxins, nutrients, and pheromones

•Estimation of biomolecules interaction and some kinetics parameters• Internal metabolic milieu, such as glucose level, oxygen level, or osmolality• Internal signal molecules, such as hormones, neurotransmitters, and cytokines•Differences between proteins of the organism itself and of the environment or alien creatures.

Acoustic, sound, vibration

Microphone

•A microphone is an acoustic-to-electric transducer or sensor that converts sound into an electrical signal.• Microphones are used in many applications such as telephones, tape recorders, hearing aids, motion picture production, radio and television broadcasting and in computers for recording voice, speech recognition, VoIP.

Force Sensors

Hydrometer

•an instrument used to measure the specific gravity (or relative density) of liquids; that is, the ratio of the density of the liquid to the density of water.•Hydrometer is used in soil analysis.

Light Sensors

• Light sensors are used in cameras, infrared detectors, and ambient lighting applications.

• Sensor is composed of photoconductors such as a photoresistor, photodiode, or phototransistor.

A typical photodiode

Seismometer

•Seismometers are instruments that measure motions of the ground, including those of seismic waves generated by earthquakes, volcanic eruptions, and other seismic sources.•Records of seismic waves allow seismologists to map the interior of the Earth, and locate and measure the size of these different sources. 

Temperature Sensor

• Temperature sensors appear in building, chemical process plants, engines, appliances, computers, and many other devices that require temperature monitoring.

Thermometer:• measures temperature or temperature gradient using a

variety of different principles.• has two important elements: the temperature sensor

(e.g. the bulb on a mercury-in-glass thermometer) in which some physical change occurs with temperature, plus some means of converting this physical change into a numerical value (e.g. the visible scale that is marked on a mercury-in-glass thermometer)

Calorimeter:•A calorimeter is an object used for calorimetry, or the process of measuring the heat of chemical reactions or physical changes as well as heat capacity.• A simple calorimeter just consists of a thermometer attached to a metal container full of water suspended above a combustion chamber.

Thermistor•A type of resistor whose resistance varies significantly with temperature, more so than in standard resistors.•thermistors can be used as current-limiting devices for circuit protection, as replacements for fuses.•thermistors are used throughout the Consumer Appliance industry for measuring temperature. Toasters, coffee makers, refrigerators, freezers, hair dryers, etc. all rely on thermistors for proper temperature control.

Proximity Sensor

•  a sensor able to detect the presence of nearby objects without any physical contact.• emits an electromagnetic field or a beam of electromagnetic radiation (infrared, for instance), and looks for changes in the field or return signal.•Used in parktronic, roller coasters, mobile devices

Pressure Sensor

Barometer

• a scientific instrument used in meteorology to measure atmospheric pressure.•Water-based barometers, mercury barometers, vacuum pump oil barometer, aneroid barometers, barographs are available

Accelerometer•An accelerometer is a device that measures proper acceleration.

Uses:•used to measure vehicle acceleration.•Camcorders use accelerometers for image stabilization.•Some smartphones use accelerometers to present landscape or portrait views of the device's screen, based on the way the device is being held.

Position sensor

Ultrasonic Sensor•used for position measurements• generate high frequency sound waves and evaluate the echo which is received back by the sensor

CO2 Gas Sensor

• CO2 sensor measures gaseous CO2 levels in an environment

•Measures CO2 levels in the range of 0-5000 ppm

•Monitors how much infrared radiation is absorbed by CO2 molecules