MAS-2 Automotive sensors and actuators.pdf

PEMP AEL2501

Automotive Sensors & Actuators

Lecture delivered by: Prof. Ashok C.Meti MSRSAS-Bangalore MSRSAS-Bangalore

M.S Ramaiah School of Advanced Studies - Ba Bangalore

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Session Objectives

• On complet completion ion of this this session session the delegates delegates would have understood : –

e var ous sensors an actuators t at are use in automotive electronics,

– Their working principles, – Their various uses in automotive automotive electronic systems


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Topics • Introdu Introducti ction on to automoti automotive ve electr electroni onics cs • Automot Automotive ive sensor sensorss and actuat actuators ors • Sele Select ctio ion n crit criter erion ion • Differ Different ent types types of sensor sensorss • Actuators ors • A cas casee stu study dy – Hond Hondaa Cit City y car car


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Automotive Autom otive Electronic Electronicss - Introdu Introduction ction • Over the past past 30 30 years, years, vehicle vehicle electronic electronic systems systems have have changed significantly. • electronic systems. • The evolutio evolution n of microco microcontroll ntroller er and and sensor sensor technology technology is allowing automobile industry to create complex complex systems that can provide higher levels of vehicle control and safety. • The The overa overall ll oal of elect electro roni nicc embed embedded ded s stem stem desi desi n is to balance production costs with development time and cost.


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Topics • Introdu Introducti ction on to automoti automotive ve electr electroni onics cs • Automot Automotive ive sensor sensorss and actuat actuators ors • Sele Select ctio ion n crit criter erion ion • Differ Different ent types types of sensor sensorss • Actuators ors • A cas casee stu study dy – Hond Hondaa Cit City y car car


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Automotive Autom otive Electronic Electronicss - Introdu Introduction ction • Over the past past 30 30 years, years, vehicle vehicle electronic electronic systems systems have have changed significantly. • electronic systems. • The evolutio evolution n of microco microcontroll ntroller er and and sensor sensor technology technology is allowing automobile industry to create complex complex systems that can provide higher levels of vehicle control and safety. • The The overa overall ll oal of elect electro roni nicc embed embedded ded s stem stem desi desi n is to balance production costs with development time and cost.


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Automotive Sensors & Actuators

• Automotive Automotive manufactur manufacturers ers are continuou conti continuously nuously sly increasing increa increasing sing the use of electronics systems to – – Safety – passenger comfort.

• Sensors Sensors and actuators actuators integrated with automotive control computers help optimize vehicle performance while im rovin reliabilit and du durabilit . Sensor-- Input Sensor

Microcontroller

Actuator Actuator-- Output


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Measurement System

ELECTRICAL OUTPUT

MEASURED QUANTITY

SENSOR

SERIAL OR PARALLEL

VOLTAGE

SIGNAL CONDITIONING

A/D

CPU

M.S Ramaiah School of Advanced Studies - Bangalore

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Selection Criteria • What is to be measured • Magnitude, range, dynamics of measured quantity • Required resolution, accuracy • Cost • Environment • Interface Requirements: – Output quantity (voltage, current, resistance,…) – – Signal conditioning – A/D requirements (#bits, data rate)


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Thermistors • Commonly used for temperature measurement on vehicles. • They are made out of semiconductor materials such as cobalt or nickel oxides. • Change in temperature causes change change in in resistance of the thermistor. • Most of the thermistors are of the negative temperature coefficient (NTC) type •

o – to a few hundred Ohms at 100o C. Thus it can be more sensitive.


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• Important factors for accurate measurements: – Supply must be constant – Current through the thermistor should be negligible ( I.e. No heating effect)

•

These devices are commonly used as sensors for – – – –

Air intake Battery Engine and transmission temperature Air conditioning and internal/external environmental temperature – Oil and gas temperatures.


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Temperature sensor • Application Engine management • Function Registration of temperature of coo ants, ue an a r • Installation Engine block, coolant circuit, air-intake tract • Sensing principle NTC technology (hot conductor, negative temperature coefficient) – Temperature range: -40°C...+150°C – Time constant: 5 s...44 s (depending on type) – Accuracy: ± 0.8 K at 100°C ±1.5 K at 20 °C


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Thermocouples • When two dissimilar metals are joined together, the thermocouple junction is formed. • Among the two junctions used, one of the junctions is kept a a cons an nown empera ure w ere as e o er a e temperature to be measured. • Ex: 70% platinum & 30% rhodium alloy known as B Type , Has a range of 0 15000C. • Used for measuring Exhaust Gas and turbocharger turbocharger temperatures in a vehicle.


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Magnetic Sensors Variable Reluctance (VR) Sensors

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Used mainly for speed and position measurements of rotating members.

( Ex:

crank shaft speed and position sensing)

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The variable reluctance sensor is an electromagnetic device consisting of a permanent permanent magnet surrounded by a winding of wire. wire

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The sensor is used in conjunction with a ferrous target that either has notches or teeth.

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Rotation of the target wheel near the tip of the sensor chan es the ma netic flux flux, creatin an analog voltage signal in the sensor coil.

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Though the voltage may vary depending on the speed of rotating member, the frequency is used for measurement.


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• A common method of converting this signal into a useful signal for interfacing w o er g a c rcu s y using a Schmitt trigger trigger circuit. • Another method is by using a quenched oscillator circuit as shown in the figure. This circuit has good resistance to .


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Typical Applications: – Ignition system engine speed and position – Speed sensing for e ectron ca y contro e transmissions – Vehicle speed sensing – Wheel speed sensing for ABS and traction control systems


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Hall Effect Transducers

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Principle: • If a certain type of crystal is carrying a current in a transverse magnetic field, then a voltage will be produced at right . • The magnitude of the voltage is proportional to the supply current and to the magnetic field strength. • With proper proper design design, the output of this device is a square wave. • The principle is used in distributors and also to detect the current flowing on a ca e.


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Variable resistance • These sensors are mainly used for sensing larger change in position. position – Example: The throttle position sensor, which is a potentiometer. • It is supplied with a stable 5 Volts DC. • The wiper is driven by the throttle shaft. shaft Thus , the voltage from the wiper contact will be proportional proportional to the throttle position. position • In many cases,throttle potentiometer is used to indicate the rate rate . implementing acceleration enrichment or over-run fuel cut-off.


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Available in clockwise and anti-clockwise

Printed Circuit Resistors M.S Ramaiah School of Advanced Studies - Bangalore

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Accelerator-pedal module • Application Engine management • Function Registering the driver's wishes eman or torque) • Installation Passenger compartment • Sensing principle Hall effect or potentiometer • Technical data – Supply voltage: 5 V – easur ng range: cus omer-spec c pe a rave 40 mm ... 80 mm – Temperature range: -40°... +80°C – Output signal: analog


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Pressure sensor • Application Engine management • Function Barometric pressure • Installation Printed circuit board (PCB) • Sensing principle Silicon micromechanics with integrated evaluation circuit • Technical data

– Measurin ran e: 60 kP... 115 kPa – Analog output: 2.37 V ... 4.54 V – Temperature range: 40°C ... +130°C M.S Ramaiah School of Advanced Studies - Bangalore

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Low-pressure sensors for gaseous media • Application Engine management • Function Registration of intake-manifold ressure or atmos heric ressure • Installation Air-intake tract •

Sensing principle Micromechanics with piezoresistive sensor element (MEMS based)

•

Technical data

– – – – –

upp y vo age: Power consumption: 9 mA (typical) Measuring range: < 400 kPa (absolute) Response time: < 1 ms Temperature range: -40°... +130°C M.S Ramaiah School of Advanced Studies - Bangalore

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Acclerometers • Piezoelectric accelerometers are generally used as knock knock sensors. • A piezoelectric accelerometer is a seismic mass accelerometer using a piezoelectric piezoelectric crystal to convert the force on the mass due to acceleration into an electrical electrical output signal. signal The piezoelectric crystal acts not only as a transducer but also as the suspension spring for the mass. • When used for knock detection, they also pick up other vibrations, these are kept at minimum by looking for a ‘knock’ a few degrees before and after the TDC.


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• The signals from this type of sensors are detected by charge amplifiers. • The sensitivity of a vehicle knock sensor is about 20mV/g ( g=9.81 m/s2). • MEMS accelerometers are replacing conventional accelerometers for – – Knock sensing – Crash sensing – INS, etc


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Knock sensor • Application Engine management • Function Registration of structure-borne vibrations (knocking). Knocking combustion can damage the engine. The data from the knock sensor enables counter-measures to be undertaken. • Installation Engine block • Sensing principle Piezo-electrical • Technical data – Sensitivity at 5 kHz: 30 ± 6 mV/g – Linearity at 5-kHz value: ± 10 % – Frequency range: 3 kHz ...22 kHz – Temperature range: -40°...+150°C M.S Ramaiah School of Advanced Studies - Bangalore

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Acceleration sensor

AEL2501

• Application – ESP® – ABS – Safety (airbag systems)

• the X, Y and Z axes • Installation – Integration into circuit board (SMD) – Remote sensor

• Sensing principle Surface mechanics (capacitive) • Technical data Measuring range (airbag) – – – –

SMD element: 2 g...250 g Peripheral sensor: 50 g...250 g Sensor output: analog or digital Temperature range: -40°C...+120°C M.S Ramaiah School of Advanced Studies - Bangalore

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Yaw-rate sensor

AEL2501

• Application ESP® • Function Registration of the rotational movement of the vehicle around its vertical axis • Installation Passenger compartment • Sensing principle Micromechanics, CAN interface • Technical data – – – – – –

Yaw-rate sensor measuring range: ±100°/s Acceleration sensor measuring range: ± 1.8 g Initialization time: <= 1.0 s Temperature range: -40°C...+85°C . ... Nominal voltage: 12 V


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Air Flow Sensor • Air flow Sensor is another example of variable resistance sensor. • When air flows in to the sensor, exerts a force on the flap which is counteracted by a calibrated spring. spring This ensures that movement of the flap is proportional to the through the sensor.


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• A slider potentiometer is connected to the flap shaft. • The resistive material used for the track is a ceramic metal mixture which is burnt into a ceramic plate at a v ery high temperature. • The potentiometer is calibrated such that the output output voltage voltage is proportional to the quantity of induced air.


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Hot wire air flow sensor • This measures air mass flow. flow • The basic principle is that as air passes over a hot wire it tries to cool the wire down. A circuit is created that tend s to increase the current through the the wire. wire This current will be proportional proportional to the air flow. • The hot-wire: – Material - Platinum – Few mm long – Dia – about 70 microns. – Time constant – very short (Small size) – Current range – 0.5 to 1.2 A – Dirt problem – Burn-off cycle at power-on or power-off .


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By-pass hot wire air flow meter


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Oxygen Sensor • The oxygen sensor provides a closed closed loop feedback for the engine management feedback system to control the air fuel ratio. ratio • The amount of oxygen sensed is directly related to the mixture strength or air-fuel ratio.

Sensor – 1 – Air/Fuel Ratio Sensor – 2 – Catalytic Converter Efficiency

• Normalized air-fuel ratio(λ ) = Current airfuel ratio / Stoichiometric air-fuel ratio . known as a Lambda (λ ) value of one. one


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• The sensor operates reliably above 300 0C. • The EGO – Exhaust Gas Oxygen sensors are heating. • In some cases, a heating element is used to bring the temperature to the working level quickly. • These heating element do not operate operate all the time. 0

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• These are called HEGO HEGO.


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• The main active component in most of the sensors is Zirconium dioxide dioxide, ZrO 2 • This ceramic material is housed in gas . 0 • At temperatures above 300 C, the zirconium dioxide will conduct negative negative oxygen ions. ions • The sensor is designed to be responsive very close to a Lambda value of 1. • Greater quantity of oxygen ions will be is exposed to reference atmospheric air.


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Through electrolytic action these ions permeate the electrode and migrate through the electrolyte. This builds up the charge charge.

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The magnitude of the charge is dependent on the oxygen % in the exhaust.

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A voltage of 400mV is the normal value at lambda value of one. one

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Most lambda sensors will cycle from rich to lean in about 50 to 100 milliseconds, and from lean to rich in 75 to 150 milliseconds. This is referred to as the "transition" time. If the O2 sensor is taking significantly longer to reverse readings, this too is an indication that it is getting sluggish and may need to be replaced.


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Actuators • ‘Actuator’ is a general term to describe a control mechanism. • An actuator is part of an openopen-loop or closedclosed-loop control system which connects the electronic unit with the process. process. • The actuator consists of a transformer and a final-control element. • Each positioning signals are converted to mechanical output.


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• A wide variety of actuators are used in control loops in an automobile • – Solenoids – DC Motors – Stepper motors – Piezo Actuators and so on..


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Solenoid Actuators •

A solenoid is defined as a coil of wire commonly in the form of a long cylinder that when carrying a current resembles a bar magnet so that a moveable core (armature) is drawn into (pulled (pulled--in) the coil when a curren ows. ows

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A more simple definition is that a solenoid is a coil and a moveable iron core used to convert electrical energy into mechanical energy.

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Normally, the movement of the core compresses a spring.

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On power-off, the armature returns back to its normal pos t on.

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The stroke of the armature varies from fraction of a mm to several mm depending on application.

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There are two main categories of solenoids: – Rotary – rotary motion of the armature – Linear – linear motion of the armature M.S Ramaiah School of Advanced Studies - Bangalore

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• Important considerations when designing a solenoid for an application: – – Force or Torque – Voltage – Current / Power – Duty Cycle – Temperature – Operating Time / Speed – Environmental – AC / DC – Life M.S Ramaiah School of Advanced Studies - Bangalore

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• One of the examples of solenoid actuator is the one used in Fuel injector. injector • A typical fuel injector solenoid has the o ow ng: – Stroke: 0.1mm – Open period range: 1.5 to 10.0 ms. – Coil resistance : 16 Ω

• Time taken by an injector to open and close is critical in fuel injection. • The induction of the coil la s an important role in the reaction time for the solenoid. (Higher inductance -> longer reaction time, ballast resistors)

• Another application of solenoid actuator is for door locks locks. M.S Ramaiah School of Advanced Studies - Bangalore

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Relays Electromagnetic switches


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DC Motors • Permanent magnet motors are commonly used in automobiles as they are versatile. – The rotary speed (RPM) of the motor which is usually high is su ta y mo e t roug gear ng own ncrease n torque or other mechanisms to get the desired rotary or linear motion.

• For applications such as power electric steering, the options available are : – Brushless DC (BLDC) – Switched-reluctance motors (SRM) – high temperature complications (automotive temperatures -40 to 125°C.)


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Typical Specifications of a DC Motor:

– Voltage: 12V DC – 10% – No load current: ≤ 4A – Load: 7650r/min± 10%, 0.226Nm, ≤ 19A – Rotation direction: clockwise


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Some of the automotive applications: – Windscreen and head light washers & wipers. – Power windows and mirrors. – Fuel pumps – Head light lifts. – Electronic Parking Brake (EPB) – Ventilation fans and so on..

• One of the draw backs of a DC motor is non-availability of direct feedback feedback. If required, one has to use variable res stor sensor to get t e necessary ee ac .


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• Ex:


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Windows Motors

Cable Window Lift Systems


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Actuat or s f or climate con tr ol Systems

EPB Actuator

Act uator s f or Lo ckin g Sys tems M.S Ramaiah School of Advanced Studies - Bangalore

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Stepper Motors • Stepping motors: – Permanent magnet Type • Permanent magnet motors usua y ave wo independent windings, with or without center taps. Center-tapped windings are used in unipolar permanent magnet motors.

– Variable reluctance Type • Variable reluctance motors usually have three (sometimes four or five) windings, with a common return.


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• Angular resolution:

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– The coarsest motors typically turn 90 degrees per step – High resolution permanent magnet motors are commonly able to handle 1.8 or even 0.72 degrees per step. – an appropr a e con ro er, mos permanen magnet and hybrid motors can be run in halfsteps, and some controllers can handle smaller fractional steps or microsteps.

• For both permanent magnet and variable reluctance stepping motors, if just one winding of the motor is energized, the rotor and then hold that angle until the torque exceeds the holding torque of the motor, at which point, the rotor will turn, trying to hold at each successive equilibrium point. • They do not have high starting starting torque. torque M.S Ramaiah School of Advanced Studies - Bangalore

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• Applications: – Idle speed air by-pass – – Speedometer display drives – Adaptive Front-lighting (AFS) system, etc. Adaptive Front-lighting System

Digital Instrument Cluster


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Piezo Actuators • •

• •

A piezo actuator enables response times of just a few Tenth of a millisecond. It consists of many crystal layers that expand by a few hundredths of millimeters when volta e is applied. One of the automotive applications of the Piezo actuators is in Diesel Unit Injection Systems. Example: – Stacked actuator • Motion up to 100 µm • Maximum load 3500 N • • Voltage -10...150V (multi-layer)


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A Case Study: HONDA City Engine Throttle Body Master Cylinder Battery

Engine (Transverse mounted)

Air Filter Alternator


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HONDA City Engine sensors IAT Sensor

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Manifold Air Temperature sensor – measures the temperature of incoming air.

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Manifold Absolute Pressure sensor – measures the –ve pressure in the inlet manifold. M.S Ramaiah School of Advanced Studies - Bangalore

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HONDA City Engine sensors Purge Control Solenoid

Throttle Body

Wiring Harness

TPS

ISC Solenoid

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Purge Control Valve – part of the evaporative emission control system.

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TPS- Throttle Position Sensor measures the throttle valve opening.

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ISC Solenoid – Idling speed control solenoid controls the flow of air during idling of engine to control the speed of engine within the specified range.


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HONDA City Engine sensors MAP Sensor

Starter Motor

Fuel Injector M.S Ramaiah School of Advanced Studies - Bangalore

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HONDA City Engine sensors

• sensors mounted on engine. • Senses the coolant temperature surroundin the en ine cylinder in the engine block.


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HONDA City Engine sensors Master Cylinder

A/C system Pressure Sensor

Brake Fluid Level sensor


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Completely assembled Porsche engine M.S Ramaiah School of Advanced Studies - Bangalore

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Cam shaft position sensor CAM Shaft

Cam shaft sensor mounting

• The cam shaft sensor is mounted on the engine near the cam shaft. • It is a Hall effect transducer which generates an electrical signal that is proportional to the rotation of the cam shaft. M.S Ramaiah School of Advanced Studies - Bangalore

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Knock Sensor Knock sensor mounting

• The knock sensor is mounted on the engine block. • It is essentially an accelerometer which generates an electrical signal that is proportional to the vibration of the cylinder block. M.S Ramaiah School of Advanced Studies - Bangalore

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Crank shaft position / Speed sensor Fly wheel

• Crankshaft position/speed sensor is mounted near the flywheel. • The flywheel will have projections that generate the pulses. • handled by the ECU to generate the necessary information.


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MAS-2 Automotive sensors and actuators.pdf

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