VRUSHABH SANGHAVI (09BEC115)

DEEP ADHVARYU (09BEC104)

UNDER THE GUIDANCE OF PROF. N. P. GAJJAR

Energy Sensors

Course Code: 2EC307 Review - 2

In Physics, energy is an indirectly observed quantity.  When matter is changed into energy (such as energy of motion, or into radiation), the mass of the system does not change through the transformation process. 

Energy is the capacity of a system to do work.The total energy contained in an object cannot be created nor be destroyed in accordance with the law of conservation of energy.

What is Energy?

What are Sensors?

A sensor is a device that measures a physical quantity and converts it into a signal which can be read by an observer or by an instrument.

 For accuracy, most sensors are calibrated against known standards.

Left: Thermocouple used as Temperature Sensor

Should be sensitive to the measured propertyShould be insensitive to any other property likely to

be encountered in its applicationDoes not influence the measured propertyIdeal sensors should be designed to be linear or linear

to some simple mathematical function of the measurement.

A good sensor obeys the following rules:

Sensor Characteristics

SensitivityRangeStabilityRepeatabilityLinearityError Response Time

Environmental FactorsEnvironmental Factors Economic FactorsEconomic Factors

Temperature RangeHumidityCorrosionSizeOver range protectionSusceptibility to EM

interferencesRuggednessPower ConsumptionSelf test Capability

CostAvailabilityLifetime

Factors taken into consideration while designing

Energy Sensors

An Energy Sensor is a device, which responds to an input quantity by generating a functionally related output usually in the form of an electrical or optical signal.

Above: Pictures Of Energy Sensors

Importance Of Energy Sensors

Sensors are pervasive. They are embedded in our bodies, automobiles, airplanes, mobile phones, chemical plants, industrial plants and countless other applications.

Sensors are used in everyday objects such as touch-sensitive elevator buttons (tactile sensor) and lamps which dim or brighten by touching the base. There are also innumerable applications for sensors of which most people are never aware. Applications include cars, machines, aerospace, medicine, manufacturing and robotics.

Sensors are needed to convert physical data available in the form of different kinds of energies for analytical and control purposes into electrical signals.

Application Of Sensors

Sensors are used in:

Fire Alarms(in picture)

Smoke Detector

OTEC (Ocean Thermal Energy Conversion)

Wind Turbine Transmission Monitoring

Wind Turbine Lubrication Systems

• Hybrid Engine Testing

• Materials and Component Testing

• Hydraulic Systems Testing

• Handling Systems for Nuclear Fuel Rods

Systems Testing

Types Of Sensors

Classification Of Energy Sensors

Sensors may be classified according to the various energies it can detect. They are:-

1. Mechanical Energy Sensors

2. Thermal Energy Sensors

3. Nuclear Energy Sensors

4. Solar Energy Sensors

5. Seismic Energy Sensors

Mechanical Energy Sensors

Mechanical Energy Sensors are the sensors that detect a change in the mechanical energy of the system.

Mechanical quantities: displacement, Strain, rotation velocity, acceleration, pressure, force/torque, twisting, weight, flow

Here we will consider sensors for displacement, velocity, acceleration, pressure.

Some of the mechanical energy sensors are:

Capacitive Accelerometer for Acceleration Sensing Piezoelectric accelerometer for Acceleration Sensing Metal foil strain-gauge based (load cell) for force sensing LVDT (Linear Variable Differential Transformer) Scanning Laser Vibratometry for velocity sensing

(a) Capacitive Accelerometer (b) Linear Variable Differential Transformer

Acceleration SensingAcceleration Sensing

Capacitive Accelerometer

Capacitive accelerometer

Good performance over low frequency range, can measure gravity!

Heavier (~ 100 g) and bigger size than piezoelectric accelerometer

Measurement range up to +/- 200 gMore expensive than piezoelectric

accelerometerSensitivity typically from 10 – 1000

mV/gFrequency bandwidth typically from 0

to 800 HzOperating temperature: -65 – 120 C

Acceleration Sensing

Piezoelectric Accelerometer

Piezoelectric accelerometer

Nonzero lower cutoff frequency (0.1 – 1 Hz for 5%)

Light, compact size (miniature accelerometer weighing 0.7 g is available)

Measurement range up to +/- 500 gLess expensive than capacitive

accelerometerSensitivity typically from 5 – 100 mv/gBroad frequency bandwidth (typically

0.2 – 5 kHz)Operating temperature: -70 – 150 C

Acceleration SensingAcceleration Sensing

Force Sensing

load cell

Metal foil strain-gage based (load cell)

Good in low frequency response

High load ratingResolution lower than

piezoelectricity-basedRugged, typically big size,

heavy weight

Piezoelectric Based Force Sensor

Piezoelectricity based (force sensor)

lower cutoff frequency at 0.01 Hz

• can NOT be used for static load measurement

Good in high frequencyHigh resolutionLimited operating temperature

(can not be used for high temperature applications)

Compact size, light

Force Sensing

Displacement Sensing

Linear Variable Differential Transformer

LVDT (Linear Variable Differential Transformer):

Inductance-based electromechanical sensor

“Infinite” resolution limited by external electronics

Limited frequency bandwidth (250 Hz typical for DC-LVDT, 500 Hz for AC-LVDT)

No contact between the moving core and coil structure no friction, no wear, very long

operating lifetimeAccuracy limited mostly by linearity

0.1%-1% typicalModels with strokes from mm’s to 1

m available

Velocity Sensing

Scanning Laser Vibratometer

Scanning Laser Vibrometry

No physical contact with the test object; facilitate remote, mass-loading-free vibration measurements on targets

measuring velocity (translational or angular)

automated scanning measurements with fast scanning speed

However, very expensive (> $120K)

Thermal Energy Sensors

The Sensor used to detect heat energy is known as Heat Energy Sensor or Thermal Sensors.

The simplest example of a heat energy sensor is a thermocouple. It provides a voltage proportional to the temperature across its junctions.

Thermal Sensors

Thermistors

Thermistors have negative temperature coefficientThey are non-metallic made of metallic oxides like manganese, nickel, cobalt or copper.The electrical resistance of material change with temperatureThey come in different forms:1.Disc type2.Washer type3.Bead type4.Rod type

ResistorThermal

Therm istor

Temperature Sensor

Bimetallic Strip

ApplicationThermostat (makes or breaks electrical connection with deflection)

Metal A

Metal B

δ

)]T-(T1[ 00 LL

Heat Flux Sensor

A heat flux sensor should measure the local heat flux density in one direction. The result is expressed in watts per square meter. The calculation is done according to:

Where Vsen is the sensor output and Esen is the calibration constant, specific for the sensor.

Heat flux sensors generally have the shape of a flat plate and a sensitivity in the direction perpendicular to the sensor surface.

Heat Flux Sensor

Heat Flux Sensor

The total heat flux is composed of a conductive, convective and radiative part. Depending on the application, one might want to measure all three of these quantities or single one out. An example of measurement of conductive heat flux is a heat flux plate incorporated into a wall.

The gold sensor only measures convective heat flux, the black sensor measures radiative as well as convective heat flux. A small air temperature sensor is added to estimate local heat transfer coefficients

Heat Flux Plate

Fire Sensing

Gardon or Schmidt Boelter gauge showing the instrument main components

a sensor sensitive to radiative as well as convective heat flux is a Gardon or Schmidt–Boelter gauge, used for studies of fire and flames.

 The Gardon must measure convection perpendicular to the face of the sensor to be accurate due to the circular-foil construction, while the wire-wound geometry of the Schmidt-Boelter gauge can measure both perpendicular and parallel flows.

Nuclear Energy Sensors

Nuclear potential energy is the potential energy of the particles inside an atomic nucleus.

This category of inventions has tremendous amount of patents.

There are a number of sensors or detectors which were invented lately to detect nuclear potential energy.

Images of Nuclear Energy Sensors from Patents filed:

Apparatus for Sensing Radioactivity

Radioactivity Sensors

Temperature and Radioactive sensors by HVAC

HVAC

 sensors are engineered to the highest standards in performance and reliability.

HVAC claims that it will help improve facility’s environment while cutting utility expenses and equipment costs

Solar Energy Sensors

The Solar Radiation Sensor, or solar pyranometer, measures solar radiation, the sum at the point of measurement of both the direct and diffuse components of solar irradiance.

Left: Dual Solar Sensor from GE Electronics Sensing

Pyranometer

Connections

The sensor’s transducer, converts incident radiation to electrical current, is a silicon photodiode with wide spectral response.

The transducer is an hermetically-sealed silicon photodiode; the included amplifier converts the transducer current into 0 to +2.5 VDC

Solar Sensor

Hukseflux Pyrheliometer DR01

Sensors from Hukseflux

Hukseflux manufactures and sells pyranometers (global solar radiation), pyrheliometers (direct solar radiation) and albedometers (solar radiation balance)The most common applications of these instruments are in measurement of the available solar energy (for use of solar radiation as a source of renewable energy), climatology (for assessing local climate and energy balance) and building physics.

Dual solar Sensor

Dual solar Sensor by GE Electronics

GE Sensors For Cars

The dual solar sensor uses two photo diode cells inside of it to measure the intensity of the light that enters into the cabin of the vehicle. It then takes this information and feeds it back to the automatic temperature control (ATC) unit of the vehicle's air conditioning system. The air temperatures of the driver's side and passenger side are then automatically adjusted up or down depending upon the amount of light entering both sides of the vehicle.

Light Sensors

A light sensor detects presence of light.

The best example of light sensor is photodiodes.

Thorlabs' C-Series Photodiode Power Meter Sensors cover a wide power and wavelength range. These sensors are offered in standard, slim, integrating sphere, and compact fiber versions to meet your specific application requirements.

Photo resistors

Photoresistors

• Light sensitive variable resistors. • Its resistance depends on the intensity of

light incident upon it. – Under dark condition, resistance is

quite high (M: called dark resistance).– Under bright condition, resistance is

lowered (few hundred ).• Response time:

– When a photo resistor is exposed to light, it takes a few milliseconds, before it lowers its resistance.

– When a photo resistor experiences removal of light, it may take a few seconds to return to its dark resistance.

Photo Resistors

Photo resistors exhibit a nonlinear characteristics for incident optical illumination versus the resulting resistance.

10 10log logR P

R

101 103102

101

104

102

103

104

Relative illumination (P)

Symbol

Seismic Energy Sensors

Seismic Sensors have shown their applicability to target bearing, range, and classification problems in the battlefield monitoring and perimeter defense system.

This kind of sensor can perform accurate measurements of small ground vibration and monitor seismic activity due to their high sensitivity to dynamic strains induced by acceleration variations.

Seismometers and Accelerometers are available for this purpose.

Seismic Sensors

Seismic Sensors by HP and Shell

Hewlett-Packard Co. and Shell announced that they are developing a new wireless sensing system for acquiring high-resolution seismic data.Improved and increasingly powerful computer technology has over the years enabled the seismic images to become increasingly precise, with the possibility of deploying thousands of sound detectors, often in a grid pattern that enables geophysicists to build a three-dimensional image of the subsurface

Microelectromechanical Systems

Seismic Sensors

Fiber Bragg grating sensors for seismic wave detection

seismic sensors based on the optical fiber Bragg grating. This kind of sensor can perform accurate measurements of the seismic activity due to their high sensitivity to dynamic strains caused by small ground vibrations.Light weight and compact125 micro centimeter in diameter

Seismic Sensors

Seismic wave detection system based on fiber optic sensor

Optical fiber sensors using fiber Bragg grating have a number of advantages such as immune to electromagnetic interference, lightweight, and low power consumption.The basic principle of the FBG seismic sensing system is that it transforms the acceleration of ground motion into the strain signal of the FBG sensor through mechanical design, and after the optical demodulation generates the analog voltage output proportional to the strain changes.

Bibliography

Materials TodayOphirWikipediaBosch Security SystemsGeneral Electronics(GE)HukesfluxThorlabsShell Corporation

HP ElectronicsEnergy max – Coherent IncPhysics TutorialSunfish Alarm SystemsElectronic Instrumentation by H S Kalsi

“Thank You”