ServiceSensors in Škoda vehiclesEngine82Protected by copyright. Copying for private or commercial purposes, in part or in whole, is not permitted unless authorised by ŠKODA AUTO A. S. ŠKODA AUTO A. S. does not guarantee or accept any liability with respect to the correctness of information in this document. Copyright by ŠKODA AUTO A. S.�Self-study programmeIntroductionNew trends in the automotive industry require new modern technologies with high reliability, low production cost, miniaturisation and high accuracy with minimal delay time. The ever-increasing demands placed on vehicles are closely associated with the dynamic development of electronics and advanced technologies.There are new control and regulating functions available not only for the control of the engine and the chassis, but also in terms of security and comfort of the occupants. In connection herewith new electronic elements, called senders, measure scalar physical quantities and vector quantities. The main requirement here is that the signals from these senders and sensors are evaluated and processed within a very short time. The vehicle is therefore capable to react to outside influences in real-time or resolve crisis situations. This brochure provides the user with theoretical information as well as practical information, where the measured variables and their measurement principles are described. Thus, it provides a complete overview of senders used in a particular unit and can at the same time be issued for all series type vehicles. Or, in contrast, the code of the individual sender can be used in order to identify the unit or type of vehicle in which the sender is installed.Protected by copyright. Copying for private or commercial purposes, in part or in whole, is not permitted unless authorised by ŠKODA AUTO A. S. ŠKODA AUTO A. S. does not guarantee or accept any liability with respect to the correctness of information in this document. Copyright by ŠKODA AUTO A. S.�2GBContentsIntroduction Vehicle sensors Term, definition, use of vehicles Classification Main requirements, trends Position sender (path, angle) Measured properties, measurement principles Throttle valve position sender Control-collar position sensor HDK Fuel gauge sender Accelerator pedal position sender Rev counter and speedometer Measured properties, measurement principles Inductive engine speed sender Speed sender and incremental turning angle sensor DWS Hall phase sensor Gearbox speed sensor RSS Needle lift sender Inductive sensor for transistorised ignition Hall sender for transistorised ignition Vibration sensors Measured properties, measurement principles Electrical signal evaluation Piezoelectric knock sensors Pressure sender Measured properties, measurement principles Protected by copyright. Copying for private or commercial purposes, in part or in whole, is not permitted unless authorised by ŠKODA AUTO A. S. ŠKODA AUTO A. S. does not guarantee or accept any liability Thick-film pressure sensors with respect to the correctness of information in this document. Copyright by ŠKODA AUTO A. S.� Micromechanical pressure sensors High-pressure sender Flow meter Measured properties, measurement principles Hot-wire air-mass meter HLM Hot-film air-mass meter HFM2 Hot-film air-mass meter HFM5 2 5 5 5 5 6 6 14 15 16 17 18 18 22 23 24 25 26 27 28 29 29 31 32 33 33 34 35 38 39 39 40 41 42GB3ContentsGas sensors, concentration meter Measured properties, measurement principles Air quality sensors Snap-action lambda probe Planar lambda probes Temperature sensor Measured properties, measurement principles Data processing, diagnostics Onboard computer, control unit Diagnostic units Summary tables Engine equipment Overview of the sensors – ENGINE Overview of the sensors – GEARBOX 44 44 45 46 47 51 51 53 53 53 54 54 56 58You will find the instructions for the assembly and disassembly, repair, diagnostics and detailed user information in the workshop manuals, the diagnostic unit VAS 505x and in the onboard literature. The time for going to press was on the 12/2009. This brochure is not subject to update.4Protected by copyright. Copying for private or commercial purposes, in part or in whole, is not permitted unless authorised by ŠKODA AUTO A. S. ŠKODA AUTO A. S. does not guarantee or accept any liability with respect to the correctness of information in this document. Copyright by ŠKODA AUTO A. S.�GBVehicle sensorsTerm, definition, use of vehiclesThe term "sender" is a synonym for the term sensor. The senders convert a physical or chemical variable Φ into an electrical variable E taking into account the interfering variables Yi. All of the following are considered variables; current, voltage and their amplitudes, frequency, periods, phases and oscillation pulse duration, "resistance", "capacity" and "inductance". A sender can be characterised by the following mathematical equations:Φ=g (E,Y1,Y2,...) E=f (E,Y1,Y2,...)SENSORY1Y2YnSP82_1Sensors and actuators are used to create the interface between the vehicle and the digital control unit that performs the processing. Relays or valves are considered actuators. The signal sent by the sender is converted into a standard by means of the circuits, which can be processed by the corresponding control unit.ClassificationIn view of the task and use, the senders are structured as follows: - function sensor, control and regulating sensor - safety and security sensor - sensors for the onboard computer of the vehicle - continuous linear - continuous nonlinear - discontinuous two-stage (snap-action sensors)Furthermore, the senders are divided according to their characteristics:Another classification criterion is the Protected by copyright. Copying for private or commercial purposes, in part or in whole, is not permitted - continuous analog (current, voltage, ...) output signalunless : authorised by ŠKODA AUTO A. S. ŠKODA AUTO A. S. does not guarantee or accept any liability with respect to the correctness of information in this document. by ŠKODA AUTO A. S. � - Copyright discontinuous two and multi-stage snap-action sensor (binary, analog, digitally coded)Main requirements, trendsRequirements high reliability low production costs operating conditions small dimension high accuracy Measures robust proven technology efficient mass production resistant encapsulation technology of miniaturisation compensation of faults in the sensorGB5Position sender (path/angle)Measured properties, measurement principlesDepending on the principle of sensing, this sender category can be divided into contact senders and contactless senders, which are not subject to wear. They are therefore more reliable and have a longer life. One drawback is its price. Angle senders are also referred to as "incremental senders" (progressive senders). In these systems, the information of the absolute position is lost when the supply voltage is turned off. Measured property Position of the throttle valve in the petrol engine Position of the accelerator pedal / the brake Path and position of the control rod in the pump Rotation angle of the flow regulator in the pump Gauge in the fuel tank - Stroke of the clutch actuator Torsion angle (torsional moment) Range 0 - 90° 0 - 30° 0 - 21 mm 0 - 60° 5 - 20 mm 0 - 50 mm 1° - 4°Potentiometric sensors The basic design elements of a potentiometer are the rotor and the resistance path, which consist either of a wire winding or a conductive carbon layer. Advantages: Disadvantages: - simple design - mechanical wear and subsequent failure Protected by copyright. Copying for private or commercial purposes, in part or in whole, is not permitted - measuring range (measuring stroke unless authorised by ŠKODA AUTO A. S. ŠKODA AUTO A. S. does not guarantee or accept any liability - problems in the liquid medium with respect to the correctness of information in this document. Copyright by ŠKODA AUTO A. S.� = supply voltage) - variable resistance between the rotor and - no electronics required the path - resistance to interference voltages - lifting the rotor in case of vibrations - noise - limited miniaturisation Usage: - turning angle sensor of throttle valve (M-Motronic) - accelerator pedal position sender, accelerator pedal module - fuel gauge sender Magnetic inductive sensors If an electrically conductive plate (Al, Cu) approaches a coil through which flows an alternating current, its active resistance as well as its inductance will both change. It is caused by eddy currents arising in the plate. Here we speak of sensors using eddy currents. In principle, sensors with a short-circuit ring typically have a soft-magnetic core consisting of sheet metals. Here the moving part is in the shape of the ring (Al, Cu).6GB12345UA(S)SSP82_21 2 3 4Damping plate Eddy currents Air-cored coil Oscillator with variable damping5 Demodulator s Measured path A(s) Voltage of the oscillator UA(s) Output voltageProtected by copyright. Copying for private or commercial purposes, in part or in whole, is not permitted unless authorised by ŠKODA AUTO A. S. ŠKODA AUTO A. S. does not guarantee or accept any liability with respect to the correctness of information in this document. Copyright by ŠKODA AUTO A. S.�12 3SP82_31 2 3 ● IW L(s) Φ(s)Short-circuit ring Soft-magnetic core Coil Current Eddy current Measured inductance path S Specified magnetic flux path SAdvantages: - linear curve over the entire length - measuring range (measuring stroke = supply voltage) - application under really extreme conditionsDisadvantages: - robust design - insensitivity to interferencesUsage: - sensor of constrictor for series pumps (installed load sensor, EDC sensor) - angle sender for the rotary injection pumpGB7Position sender (path/angle)The last representative of the magnetic inductive sensors is the sender with plunger, which works on the principle that the inductance of the coil changes by means of a movable core. It is made of solid iron (wire), rolled plate or ferrite.1 234 51 2 3 4 L(s) φSP82_4Multi-chamber coil Ferrite core Plastic press-in part with sliding-block guide Rotational axis with pilot pin 5 Measured inductance path S Measured angleUsage: - angle sender for the rotary injection pumpMagnetostatic sensors If the magnetic induction B passes vertically through a thin semiconductor wafer fed by an electrical current, the Hall voltage UH, which is directly proportional to the size of the magnetic field, can be measured perpendicularly to the flow direction. This phenomenon is called the Hall effect . At the same time, however, the resistance of the wafer increases, which is called the Gauss effect - magnetoresistance. The Hall sender eliminates the disadvantages of the inductive sensors, using the rotating flow principle "Spinning Current", whereby the production cost is also minimal.Switching arrangement B Magnetic induction ● Current through the wafer IH Hall current IV or in whole, Supply current Protected by copyright. Copying for private or commercial purposes, in part is not permitted unless authorised by ŠKODA AUTO A. S. ŠKODA AUTO A. S. does not guarantee or accept any liability UR by ŠKODA Longitudinal with respect to the correctness of information in this document. Copyright AUTO A. S.� voltage α Engine displacement by the magnetic fieldSP82_58GBSP82_5Curve of Hall voltage UHIncrease in resistance R of the wafer (Gauss effect)Protected by copyright. Copying for private or commercial purposes, in part or in whole, is not permitted unless authorised by ŠKODA AUTO A. S. ŠKODA AUTO A. S. does not guarantee or accept any liability with respect to the correctness of information in this document. Copyright by ŠKODA AUTO A. S.�a1 2 3Rotational phase φ1SP82_6b 1 2 3 ● UHRotational phase φ2 = φ1 + 45° Semiconductor wafers Active electrode Passive electrode Supply current Hall voltageGB9Position sender (path/angle)Differential Hall senders - "Gradient sensors" Version in which two Hall senders are arranged side by side on one chip at a certain distance, whereby the difference of both voltages is evaluated electronically. Only the "gradient of the magnetic field" is sensed.12 341 2 3 4SP82_7Ring gear Integrated differential Hall circuit Homogenised wafer Permanent magnetUsage: - speed measurement Angle sender for the range up to 180° It consists of the magnetic disc of the rotor, two fixed elements to guide the magnetic flux and the Hall sender, which is located between them. The magnetic flux depends on the angle of rotation of the rotor.4 1 5231 2 3 4 5 646SP82_8Motor pulley (permanent magnetic) Pin attachment Element for guiding the magnetic flux Air gap Hall sender Axle (soft-magnetic)Disadvantage: - low shielding from external fields Usage: - accelerator pedalProtected by copyright. Copying for private or commercial purposes, in part or in whole, is not permitted unless authorised by ŠKODA AUTO A. S. ŠKODA AUTO A. S. does not guarantee or accept any liability with respect to the correctness of information in this document. Copyright by ŠKODA AUTO A. S.�10GBAngle sender for the range above 180° It consists of a fixed plate which is equipped with n Hall senders and a cover with the corresponding number of magnets. Between them there is a magnetic sensor, during the rotation n of this sensor different codewords are generated.1231 2 3Housing with permanent magnets Encoding disc Board with the Hall sendersSP82_9Usage: - speed measurement - turning angle of the steering wheel Differential magnetoresistive sensors The principle, on which the sensor works, describes the Gauss effect. The resistor is made of an InSb semiconductor, in short-form, so that it has a very low resistance.In order to achieve useful values (of the order of kΩ), a large number of plates must be connected in series. The operating temperature is almost 200ºC. A small conductive element, which excites both resistors of the sensor, moves via the sensor in order to sense the path or the angle.4 1 2 311 Magnetoresistance R1,2 2 Soft-magnetic substrate Protected by copyright. Copying for private or commercial purposes, or in whole, is not permitted 3 in partPermanent magnet unless authorised by ŠKODA AUTO A. S. ŠKODA AUTO A. S. does not guarantee or accept any liability 4 Toothed gear with respect to the correctness of information in this document. Copyright by ŠKODA AUTO A. S.� UA Supply voltage SP82_10 U0 Output voltageAdvantage: - high signal level - no evaluation electronics required - immune to external magnetic fieldsGBUsage: - speed sender11Position sender (path/angle)Magnetoresistive (NiFe) AMR thin-film sensors (Anisotropic Magneto Resistive) The electrical resistance of the thin conducting layer is "anisotropic," i.e. it is higher in the direction of the vector of magnetisation. In order to indicate this direction of magnetisation, the sensors are provided with a weak magnet. The cosine path of the resistance or the voltage results from the rotation of the vector. The control magnetic field B is formed by the rotary magnet via the sensor. A high sensitivity is achieved by forming a "bridge" made of four resistors AMR. The remaining accuracy is achieved by switching two bridges in series and by the rotation of 45°.1a 1 22Measurement principle Permalloy resistors Rotating permanent magnet with control induction BSP82_11b 3 4 a b UA U0 φCharacteristics Low operating temperature High operating temperature Linear measuring range Usable measuring range Output voltage Supply voltage (=5V) Rotation angleRotation angle φ unless authorised by ŠKODA AUTO A. S. ŠKODA AUTO A. S. does not guarantee or accept any liabilitywith respect to the correctness of information in this document. Copyright by ŠKODA AUTO A. S.�Protected by copyright. Copying for private or commercial purposes, in part or in whole, is not permittedSP82_1212GBBridge circuit B Control induction lV Supply current UH1,H2 Measured voltages φ Rotation angleSP82_13Arrangement of two bridges integrated into one another, rotated by 45°SP82_14Protected by copyright. Copying for private or commercial purposes, in part or in whole, is not permitted unless authorised by ŠKODA AUTO A. S. ŠKODA AUTO A. S. does not guarantee or accept any liability with respect to the correctness of information in this document. Copyright by ŠKODA AUTO A. S.�GB13Position sender (path/angle)Magnetoresistive multilayer GMR sensors (Giant Magneto Resistance)By applying the magnetic field, a 50% change in resistance occurs in the multiple layers, which is much larger than that of AMR sensors. Advantage: - much greater measuring effect - clear identification of the rotation angle121SP82_151 2 B φFe layers Thin antiferromagnetic layers CuCo Control induction Rotation angleThrottle valve position senderStructure and function principle The fixed part consists of two resistance wires, driven by two rotors, thus forming together with the leg the rotation element which is firmly connected to the shaft of the throttle valve. The angle of rotation is directly proportional to the ratio UA /UV, whereby the operating voltage UV = 5V. The characteristics of the sender is linear.1 2 3 45SP82_171 2 3 4 5Throttle valve shaft Resistive path 1 Resistive path 2 Leg with the rotors Electrical connection (4 pin)Protected by copyright. Copying for private or commercial purposes, in part or in whole, is not permitted unless authorised by ŠKODA AUTO A. S. ŠKODA AUTO A. S. does not guarantee or accept any liability with respect to the correctness of information in this document. Copyright by ŠKODA AUTO A. S.�Usage: The throttle valve position sender senses the rotation angle of the throttle valve of the petrol engine. On engines with the M-Motronic system, the function of recognition of the working ranges, such as idle, full load, emergency mode is used as supplementary information. The ME-Motronic system provides the required torque by means of this sender.14GBControl-collar position sensor HDKStructure and function principle The senders have a core made of soft-magnetic iron sheets. At one end is the measuring coil and at the other end the reference coil. When the alternating current passes through the coils from the control unit, alternating magnetic fields occur. The reference ring is immobile, while the measurement ring is attached on the control rod or on the shaft of the control spool. When the measurement ring moves, the magnetic flux changes and with it the voltage. The evaluation circuit forms the ratio of the input and reference voltage UA /URef. The characteristics of the sender is linear.3 126 451 2 3 4 5 6 sSP82_18Soft-magnetic core Reference coil Reference short-circuit ring Control rod Measuring coil Measuring short-circuit ring Path of the control rod12341 Measuring coil 2 Measuring short-circuit ring Protected by copyright. Copying for private or commercial purposes, in part or in whole, is not permitted unless authorised by ŠKODA AUTO A. S. ŠKODA AUTO A. S. does not guarantee or accept any liability 3 Soft-magnetic core with respect to the correctness of information in this document. Copyright by ŠKODA AUTO A. S.� 4 Shaft of control spool 5 Reference coil 6 Reference short-circuit ring φmax Angle adjustment range of the shaft for the control spool φ Measured angle5 6SP82_19Advantage: - are very accurate and robust - not subject to wear Usage: - position sender of the regulator for sensing the position - angle sender in the fuel flow regulator for the rotary injection pumps.GB15Position sender (path/angle)Fuel gauge senderStructure The sender consists of an encapsulated potentiometer, which is sealed against the penetration of fuel and used as a variable resistor. The fixed part of the potentiometer has two resistance paths, resistors and connectors. The rotating part is the shaft that connects the leg of the rotor with the float lever. Function principle The spring of the rotor moves via the resistance paths of the potentiometer while the fuel level changes. This angle of rotation of the float is transmitted as voltage. The end stops define the rotation range of 100° for the minimum and maximum level while preventing the occurance of noise at the end of the path. The operating voltage is 5-13V.12 3 45 6Protected by copyright. Copying for private or commercial purposes, in part or in whole, is not permitted unless authorised by ŠKODA AUTO A. S. ŠKODA AUTO A. S. does not guarantee or accept any liability with respect to the correctness of information in this document. Copyright by ŠKODA AUTO A. S.�79 8SP82_201 2 3 4 5 6 7 8 9Electrical supply lines Rotor spring Contact rivet Board with resistors Shaft of the potentiometer (mounted) Double contact Float lever Float Fuel tank bottomUsage: It is the task of the sender for the fuel supply in the tank to monitor the current status and transmit the appropriate signal to the control unit. It is installed in the tank as a built-in module together with the fuel pump, the filter, etc. In this version, it is supplied for petrol engines as well as for diesel engines.16GBAccelerator pedal senderStructure and function principle Potentiometric accelerator position sender The main component is the potentiometer, on which the voltage is set depending on the position of the pedal. The control unit then converts this voltage into the relative path, possibly into the angle position. For diagnostic purposes, a redundant (dual) sender is integrated, which transmits two independent signals. Hall angle sender It is derived from the principle of the moving magnet and has a range of 90°. The magnetic flux of the rotor, shaped as a magnetic disc, flows through the pin attachment (2), two other elements for guiding the magnetic flux (3) between which the Hall sender ASR1 is located, as well as the axle (6) and back to the rotor. The magnetic flux is dependent on the angular position φ. The type ASR2 does not have two magnetic elements for directing the magnetic flux.123 456SP82_211 2 3 4 5 6Housing lock Rotor pulley (permanent magnetic) Evaluation electronics with Hall sender Lower part of housing Return spring Control element (e.g. toothed gear)Usage: The driver operates the throttle valve of the petrol engine or the injection pump of the diesel engine mechanically via a control cable or a tie rod when actuating the accelerator pedal. Protected by copyright. Copying for private or commercial purposes, in part or in whole, is not permitted In electronic systems the engine management, the accelerator pedal position sender takes unless of authorised by ŠKODA AUTO A. S. ŠKODA AUTO A. S. does not guarantee or accept any liability with respect to the correctness of information in this document. Copyright by ŠKODA AUTO A. S.� over the function of the mechanical connection.GB17Rev counter and speedometerMeasured properties, measurement principlesThe rev counter and speedometer measure the angle or the path per unit time. If the motion of the vehicle compared to the basic reference system, which is the area, is measured, we get "absolute variables". In the event that we follow the motion of two systems located in this area, we measure the "relative variables". The senders of the relative rotational speed can be divided according to the number of sensed markings on the periphery of the rotor, as follows:a) b) c)SP82_22Incremental sender - with a fine pitch for precise immediate sensing. Segment sender - where the division corresponds to the number of controlled elements. Ordinary senders - which sense the mean speed of rotation with the single marking.Usage: - speed of the crankshaft and camshaft - speed of the wheels (ABS / TCS / ESP) - speed of the injection pump - measurement by means of senders directly integrated in the bearings (at the wheel or at the crankshaft) - speed in relation to the ground - rotational speed of the vehicle in relation to the tilt or pitch axis (protection against overturning) For practical reasons, senders which work on magnetic principles are preferred and are Protected by copyright. Copying for private or commercial purposes, in part or in whole, is not permitted unless authorised by ŠKODA AUTO A. S. ŠKODA AUTO A. S. does not guarantee or accept any liability divided according to their form as follows:with respect to the correctness of information in this document. Copyright by ŠKODA AUTO A. S.�- rod-shaped sensors - bifurcated sensors - circular sensors Thus the rotor is of critical importance when measuring the speed and exists in practice usually in the form of gear wheels. A tooth which has been removed partially or entirely is used as a "reference marking". In addition to the gear wheels, pressed discs with openings or wavy rings are used. Pioneering was the introduction of senders, which are directly integrated in the bearing, whereby the rotor consists of wheels with a small number of poles. These are then sensed by means of Hall senders.18GBRelative measurement of the speed and the acceleration Inductive sensors The basic principles are described in chapter 2.1. They consist of a rod magnet (1) with pin attachment (2), at which an induction coil (3) with two outputs is located. If a ferromagnetic rotor (5), which is provided with a marking (6), rotates in front of the sender, a directly proportional voltage is induced in the coil on the basis of the change in magnetic flux relating to this change.12 3 4 6 5SP82_231 2 3 4 5 6 λRod magnet Soft-magnetic pin attachment Induction coil Air gap dL Ferromagnetic toothed gear (or rotor, if necessary, pulse wheel) Peripheral or reference marking Tooth spacingAdvantages: - low production costs - resistance to external magnetic fields - dynamic measurement principle - wide temperature rangeDisadvantages: - problem with the miniaturisation - dependence of the output signal from the speed - sensitivity to the variations in air gapProtected by copyright. Copying for private or commercial purposes, in part or in whole, is not permitted unless authorised by ŠKODA AUTO A. S. ŠKODA AUTO A. S. does not guarantee or accept any liability with respect to the correctness of information in this document. Copyright by ŠKODA AUTO A. S.�Usage: - inductive engine speed sender (the crankshaft) - inductive wheel speed sender - needle movement sender (diesel injection)Magnetostatic sensors The basic principles are described in chapter 2.1. The output signal from these senders is not dependent on the speed of the rotor, but only on the intensity of the field. An advantage is the miniaturisation and a disadvantage is the low resistance of the electronics to high temperatures.GB19Rev counter and speedometerHall barriers The "integrated Hall circuit" is designed for temperatures ≤ 150°. It is located in a closed magnetic circuit, which consists of the magnet and the pin attachments. The rotor forms a magnetically passive bezel, located in the air gap. This interrupts the magnetic flux at the appropriate time, whereby the voltage is also interrupted, and subsequently the signal is evaluated.SP82_24SP82_25Tubular Hall sender Once again, the sensed element is the rotor, which can be either magnetically active or passive (magnet wheel). In the passive version, the magnetisation depends on the air gap, which can cause erroneous pulses.12 35SP82_26Passive rotor 1 Incremental rotor 2 Integrated Hall circuit 3 Permanent magnet 5 Housing φ Rotation angleProtected by copyright. Copying for private or commercial purposes, in part or in whole, is not permitted unless authorised by ŠKODA AUTO A. S. ŠKODA AUTO A. S. does not guarantee or accept any liability with respect to the correctness of information in this document. Copyright by ŠKODA AUTO A. S.�4 25SP82_27Active rotor 2 Integrated Hall circuit 4 Magnet wheel 5 Housing φ Rotation angle20GBGradient sensor They are created on the basis of differential Hall senders or magnetoresistive differential senders and are much more suitable for sensing magnetically passive rotors than Hall senders. The basic principles are described in chapter 2.1. The sender measures the difference in the intensity of the field in two points. The first point is located directly under the tooth and the second point in the gap. Tangential sensors They are either produced with thin-film technology AMR (Section 2.1) or as simple permalloy resistors with full or half bridge circuit. However, they require an integrated amplifier.13Protected by copyright. Copying for private or 2commercial purposes, in part or in whole, is not permitted unless authorised by ŠKODA AUTO A. S. ŠKODA AUTO A. S. does not guarantee or accept any liability with respect to the correctness of information in this document. Copyright by ŠKODA AUTO A. S.�1 2 3 Bφ U0 UASP82_28toothed gear (Fe) Permanent magnet Sender Intensity of the control field with tangentialcomponent Bt and radial component Br Rotation angle Supply voltage Measured voltageSensing elements GMR The basic principles are described in chapter 2.1. Usage: - Hall sender (transistorised ignition TZ-H) - Hall phase sensor (of the camshaft) - Hall sender at the gearbox - Active Hall speed sender - Active speed sender AMR - Magnetoresistive sensor (for the injection pumps of diesel engines with radial piston)GB21Rev counter and speedometerInductive engine speed senderStructure and function principle The pulse wheel (7) is exposed to magnetic field via the pin attachment (4) which is connected to the magnet (1). The attachment also forms the core of the coil (5). The intensity of the magnetic flux through the coil is dependent on whether there is a tooth or a gap in front of the Hall sender. These changes in magnetic flux induce an output voltage in the coil, which then is directly proportional to the changes in speed. The pulse wheels for petrol engines usually have 60 teeth, two of which are omitted. Another version used in diesel engines is a wheel that has all around one tooth for each cylinder. In the case of the PD engines (pump-nozzle) the markings are made depending on the type of engine. There are four teeth in a four-cylinder engine, i.e. four pulses per rotation.1 2 34 5 6 71 2 3 4 5 6 7Permanent magnet Sender housing Engine housing Pin attachment Winding Air gap Pulse wheel with reference markingSP82_29Usage: The senders are used for measuring the engine speed as well as to determine the position of the crankshaft. The speed is calculated based on the time interval of the signals of the sender.22Protected by copyright. Copying for private or commercial purposes, in part or in whole, is not permitted unless authorised by ŠKODA AUTO A. S. ŠKODA AUTO A. S. does not guarantee or accept any liability with respect to the correctness of information in this document. Copyright by ŠKODA AUTO A. S.�GBSpeed sender and incremental turning angle sensor DWSStructure and function principle The rotor consists of the toothed pulse wheel with 120 teeth, which is mounted on the drive shaft of the pump. The tooth gaps correspond to the number of cylinders of the engine. A double magnetoresistive differential sender is used for sensing. It is a magnet type sender with its pole face homogenised with a thin ferromagnetic wafer. On this there are four magnetic resistors that withstand temperatures of up to 170°C. Two of them are alternately located opposite the teeth and two opposite the gap. They are electrically connected to a full bridge.12 3 4 3 5 3 63SP82_301 2 3 4 5 6Elastic film with transmitters Speed sender / turning angle sensor Tooth gap Toothed pulse wheel Rotating bearing ring Drive shaft1 2 3 4SP82_31Protected by copyright. Copying for private or commercial purposes, in part or in whole, is not permitted unless authorised by ŠKODA AUTO A. S. ŠKODA AUTO A. S. does not guarantee or accept any liability with respect to the correctness of information in this document. Copyright by ŠKODA AUTO A. S.�1 2 3 4Magnet Homogenised wafers (Fe) Magnetoresistance Toothed pulse wheelGB23Rev counter and speedometerHall phase sensorStructure and function principle Rod-shaped Hall sensor The principles are described in chapter 2.1. The integrated Hall circuit (6) is located between the rotor made of ferromagnetic material (7) and the magnet (5), which forms the magnetic field. If a tooth approaches a semiconductor wafer, the intensity of the field changes and a Hall voltage of a size of several mV occurs. The integrated evaluation electronics, itself integrated in the Hall circuit, processes the signal and transmits a rectangular pulse to the output.1 2A3 4 5 6Position of the sender and the unidirectional pulse wheel Electrical connection (connector) Sender housing Engine housing Sealing ring Permanent magnet Integrated Hall circuit Pulse wheel with teeth (Z) and gap (L) Air gap Rotation angle71 2 3 4 5 6 7 a φSP82_32BCurve of output voltage UAProtected by copyright. Copying for private or commercial purposes, in part or in whole, is not permitted unless authorised by ŠKODA AUTO A. S. ŠKODA AUTO A. S. does not guarantee or accept any liability with respect to the correctness of information in this document. Copyright by ŠKODA AUTO A. S.�24GBRotation angle φSP82_33Usage: The position of the camshaft specifies whether the moving piston located in the upper turning point is in the compression stroke or in detent. The sender of the camshaft, which is also called "phase sensor" transmits this information to the control unit.Gearbox speed sensor RS (Rotational Speed Sensor)Structure and function principle The active speed sender has an integrated differential Hall circuit, which must be connected to the voltage source UV. The rotor can be a toothed gear, a magnet wheel or a pressed sheet metal. The senders are available in two versions. The first provides a rectangular speed signal. In the second version, the signal is extended by additional information relating to the rotation direction, the detection of the idle state, the reserve of the air gap and the mounting position. Usage: These senders are designed so that they can resist the working environment, in this case oil, in which they are immersed, as well as higher temperatures, ranging from -40 to +150°C. The supply voltage UV is 4.5 – 16.5V.GBProtected by copyright. Copying for private or commercial purposes, in part or in whole, is not permitted unless authorised by ŠKODA AUTO A. S. ŠKODA AUTO A. S. does not guarantee or accept any liability with respect to the correctness of information in this document. Copyright by ŠKODA AUTO A. S.�25Rev counter and speedometerNeedle lift senderStructure and function principle The permanent magnetic pressure bolt is pushed into the coil, which induces a directly proportional voltage to the moving speed as a result of the change in the magnetic flux.12 83 4 5 6Protected by copyright. Copying for private or commercial purposes, in part or in whole, is not permitted unless authorised by ŠKODA AUTO A. S. ŠKODA AUTO A. S. does not guarantee or accept any liability with respect to the correctness of information in this document. Copyright by ŠKODA AUTO A. S.�71 2 3 4 5 6 7 8SP82_37Body of the holder Needle movement sender Pressure spring Guide ring Pressure spring Pressure spindle Nut for clamping the nozzle Port for the evaluation circuitUsage: The start of the injection is an important variable for the optimal functioning of diesel engines. Its sensing allows the conversion of the injection, depending on the load and speed. The holder of the nozzle with the needle lift sender NBS serves this purpose, for standard injection pumps as well as for rotary pumps. By lifting the needle on the nozzle, the sender transmits a signal that is further processed.26GBInductive sensor for transistorised ignitionStructure The sensor is located in the body of the distributor. The soft-magnetic (conductive) core of the coil with the winding, has the shape of a circular disc and is called "pole plate". Together with the magnet they form a complex, the so-called stator. The pulse wheel, known as the rotor and made of soft-magnetic steel, is fitted on the shaft of the distributor. The core and the rotor have attachments in the form of teeth, whose number correspond with the number of cylinders in the engine. Function principle During the rotation of the rotor, the width of the air gap between both attachments changes periodically, which leads to a change in magnetic flux. This change induces an AC voltage in the coils whose magnitude is directly proportional to the speed. The voltage frequency f corresponds to the number of sparks per minute.f = z • n/2 f - frequency (min-1) z - number of cylinders n - engine speed (min-1)SP82_38Signal voltage USProtected by copyright. Copying for private or commercial purposes, in part or in whole, is not permitted unless authorised by ŠKODA AUTO A. S. ŠKODA AUTO A. S. does not guarantee or accept any liability with respect to the correctness of information in this document. Copyright by ŠKODA AUTO A. S.�TimeSP82_39Usage: The sensor serves to initiate the spark for the transistorised ignition. It is an electrical AC generator.GB27Rev counter and speedometerHall sender for transistorised ignitionStructure The Hall sender is in the distributor and its integrated circuit is cast in plastic, for reasons of humidity, mechanical damage and contamination. Magnetically conductive elements and the rotor with the bezels are made of soft-magnetic material. The number of bezels correspond to the number of cylinders of the engine. Function principle The bezels of the rotor move without contact in the air gap. If the air gap is free, the magnetic field passes through the integrated Hall circuit and the voltage reaches its maximum, whereby the integrated circuit is connected. If one of the bezels penetrates the gap, it prevents the passage of the magnetic field and thus the voltage reaches its minimum.1 2a 31 2a 2b 3 4 USSP82_4042bAperture with width b Permanent magnet Elements for guiding the magnetic flux made of soft-magnetic material Integrated Hall circuit Air gap Signal voltage (adapted Hall voltage)Signal voltage USProtected by copyright. Copying for private or commercial purposes, in part or in whole, is not permitted unless authorised by ŠKODA AUTO A. S. ŠKODA AUTO A. S. does not guarantee or accept any liability with respect to the correctness of information in this document. Copyright by ŠKODA AUTO A. S.�TimeSP82_41Usage: The "Hall barrier" serves to initiate the spark for the transistorised ignition TZ-H.28GBVibration sensorsMeasured properties, measurement principlesVibration sensors are suitable for controlling the knocking in internal combustion engines. Vibration sensors work according to the same principle as acceleration senders. The measured property is thus the acceleration a, which is given as a multiple of gravitational acceleration g (g = 9.81 ms-2). The measurement is based on the fundamental law of mechanics: F=m•a This has the result that the acceleration of the body a depends on its mass m and the force F, acting on it. Depending on the nature of the measured property, vibration sensors can be divided into two systems: - systems for measuring the path - systems for measuring the mechanical tensionSystems for measuring the mechanical tensionPiezoelectric materials create charges on their surfaces Q under the influence of mechanical stresses caused by external forces F. Electrodes are attached to the surface. Natural crystalline materials exhibit this property naturally. Man-made materials must be polarised by means of an electric field for this purpose. As a result of the influence of the environment, "depolarisation" can occur which changes the structure of the material and this principle does no longer work. One of the possibilities may be if the "Curie temperature" of 160°C is exceeded or a mechanical influence, such as intense vibrations. Another negative characteristic which present all man-made materials is the "pyroelectric effect" which produces charges in the materials due to the change in temperature. These charges are independent of the duration of the effect of the external force and are diverted over time via the measuring circuit or they discharge. Thus the sensors cannot measure statically, but dynamically.Protected by copyright. Copying for private or1 commercial purposes, in part or in whole, is not permitted unless authorised by ŠKODA AUTO A. S. ŠKODA AUTO A. S. does not guarantee or accept any liability with respect to the correctness of information in this document. Copyright by ŠKODA AUTO A. S.�21SP82_421 2 l A F Q U ε dElectrodes Piezoelectric model Length Cross-sectional area of the model Force Charge Voltage Dielectric constant Piezoelectric charge constantGB29Vibration sensorsThe electrical behaviour of these sensors is described by the "piezoelectric charge constant d" or by the "piezo module K". Here are the following relations:Mechanical tensionσ=F/A(N/m2 )Variable of the charge Q = d • F (C) Sender voltage U = g • L • σ (V) Intensity of the electric field E = g • σ (V/m ) Piezoelectric voltage constant F A L ε force (N) cross section of the body (m2) length of the body (m) dielectric constant g = d/ εDepending on the type of stress, the piezoelectric effect can further be divided into the longitudinal effect (a), the longitudinal sliding effect (b) and the lateral sliding effect. Each of them finds here its application in practice.SP82_43Thin PVDF films They are among the most widely used, man-made materials in the automotive industry. Advantages: Protected by copyright. Copying for private or commercial purposes, in part or in whole, is not permitted Disadvantages: unless authorised by ŠKODA AUTO A. S. ŠKODA AUTO A. S. does not guarantee or accept any liability - very low cost with respect to the correctness of information in this document. Copyright by ŠKODA AUTO A. S.� - poor measurement properties - pyroelectric effect30GBBimorph wafers They consist of two piezoelectric ceramic wafers with opposite polarisation sense. While bending, one layer will be stretched (ε 0) and the other is compressed (ε 0). The resulting voltage equals the sum of the partial voltages of both layers. If one of the ends is firmly anchored, the curvature can be measured. If they are soldered or glued to a metal diaphragm, they also measure the deflexion.1 1SP82_44At rest 1 F U U1,2When bending,stretching above (ε 0), pressing below (ε 0) Polarisation direction Measured force Total voltage Partial voltageElectrical signal evaluationVoltage sensing Charge sensing11 2 2SP82_45SP82_461 2 Cm F Q UPower cable Piezoelectric model with capacity Cp Measured capacity Measured force Charge VoltageUsage: - Hall-acceleration sender - Piezoelectric acceleration sender (bimorph bending elements, longitudinal elements as knock sensor) - Micromechanical acceleration sensorGBProtected by copyright. Copying for private or commercial purposes, in part or in whole, is not permitted unless authorised by ŠKODA AUTO A. S. ŠKODA AUTO A. S. does not guarantee or accept any liability with respect to the correctness of information in this document. Copyright by ŠKODA AUTO A. S.�31Vibration sensorsPiezoelectric knock sensorsStructure On account of its inertia, the mass exerts compressive forces on a circular piezoceramic element in the same rhythm as the vibrations causing them. As a result of the deformation, charge transfer occurs within the ceramic element. A voltage is generated between the upper and lower sides of the ceramic element, this voltage is increased with an AC amplifier and is further processed in the control unit of the ignition. Installation The following conditions must be observed so that the resulting signals can be directed from the measuring site to the sender which is mounted with one screw: - The screw must be tightened to relevant tightening torque. - The mounting surface and the thread opening in the engine must have the required quality. - No balancing or spring washers must be used for mounting.1 234Protected by copyright. Copying for private or commercial purposes, in part or in whole, is not permitted unless authorised by ŠKODA AUTO A. S. ŠKODA AUTO A. S. does not guarantee or accept any liability with respect to the correctness of information in this document. Copyright by ŠKODA AUTO A. S.�5 67SP82_471 2 3 4 5 6 7 VPiezoceramic Seismic mass with pressure forces F Housing Screw Port Electrical connection Engine block VibrationUsage: Regarding their principle of functionality, knock sensors are basically vibration sensors and are suitable for detecting structure-borne acoustic oscillations. The sensor converts the deflections into electrical signals.32GBPressure senderMeasured properties, measurement principlesThe pressure is measured directly by means of the diaphragm deformation or by a force sensor. For the measurement, sensors are used which are suitable for measuring static, as well as dynamic systems, that are not only in gaseous or liquid state, but also thoses which are made of soft gel-like substances. Diaphragm sensors The most common method of pressure measurement uses a thin diaphragm as a mechanical intermediate stage, which is exposed on the one side to the pressure to be measured, as a result of which it flexes. Capacitive sensors Direct contact with the medium to be measured is necessary. It requires expensive technical measures to separate the sensor from this medium. A measuring element of the capacity may be a capsule. SGS measurement (StrainGaugeStrip) Depending on the type of the diaphragm, the SGS measurement can be divided into the following measurement techniques. bonded films thick layer metal sheeting thin siliceous layer diffused resistorsTheir properties differ substantially depending on their size and measuring effect. The size of the measuring effect characterises the "coefficient K", which indicates the relative change of resistance R in terms of relative value of its length l.Coefficient K Resistance Poisson constant Electrical conductivityK=ΔR/R Δρ/ρ =1+2•ν+ ε ε R (Ω)ν ρ (S) Siemens Δl (ppm) l Δw (ppm) wLongitudinal extension ε = Transverse extension ε=Protected by copyright. Copying for private or commercial purposes, in part or in whole, is not permitted unless authorised by ŠKODA AUTO A. S. ŠKODA AUTO A. S. does not guarantee or accept any liability with respect to the correctness of information in this document. Copyright by ŠKODA AUTO A. S.� SP82_48GB33The materials used for the diaphragms are either ceramic, metallic or made of quartz (silicon). The deflection of the diaphragm is established by different strengths of pressure forces on both sides. The fundamental division of pressures for the senders, are: absolute pressure reference pressure barometric pressure differential pressure (pressure difference)Return to the force sensor These sensors are designed so that the force resulting from the bending of the diaphragm is transmitted to the force sensor by means of an extension rod. Usage: - thick-film pressure sensors micromechanical pressure sensors - silicon pressure sensor in the combustion chamber high pressure sender with metal diaphragmThick-film pressure sensorsStructure and function principle The sensor is divided into a measuring cell and the space for the evaluation circuit. Both parts are arranged on a common ceramic substrate. The measuring cell consists of a thick-layered diaphragm, near which purposes, are four resistances in the bridge circuit. Two active Protected by copyright. Copying for private or commercial in part or in whole, is not permitted unless authorised by ŠKODA AUTO A. S. ŠKODA AUTO A. S. does not guarantee or accept any liability resistors change their conductivity according to the mechanical and two passive rewith respect to the correctness of information in this document. Copyright by ŠKODA AUTO A. S.tension � sistors serve as temperature compensation. The deflection of the diaphragm causes a change in the balance of the bridge circuit and the measured voltage UA, which is fed into the control unit, and corresponds to the measured pressure p.1 2 3 4 4 2 51 2 3 4 5 pSP82_49Thick-layered diaphragm Passive reference tenacity Reference pressure chamber (blister) Active tenacity Ceramic substrate Measured pressure34GBPressure sender1 2 3 4 5Measuring section: 1 Pressure port for the measured pressure p 2 Measuring cell 3 Sealing partitionSP82_50Signal processing: 4 Evaluation circuit 5 Thick-layer hybrid circuit on ceramic substrateA B C U0 UM UASP82_51Measuring cell SGS Amplifier Temperature compensation circuit Supply voltage Measured voltage Output voltageUsage: Thick-film pressure sensors are used occasionally as an alternative to micro-mechanical senders. - pressure sender in intake manifold and charge pressure sender (20 - 400 kPa) Protected by(60 copyright. Copying for private or commercial purposes, in part or in whole, is not permitted - ambient pressure sender - 115 kPa) unless authorised by ŠKODA AUTO A. S. ŠKODA AUTO A. S. does not guarantee or accept any liabilityMicromechanical pressure sensorswith respect to the correctness of information in this document. Copyright by ŠKODA AUTO A. S.�Version with reference vacuum on the structure side Structure The measuring cell consists of a silicon chip. A thin diaphragm, on which four resistors are diffused, is etched micromechanically into the chip. Its electrical resistance changes depending on the mechanical tension of the diaphragm. The reference vacuum is located under the cap. A temperature sensor is often integrated in the housing of the sender, its signal is evaluated independently. Function principle The measuring resistors are connected as a bridge. By changing the resistors, the ratio of the electrical voltage changes on the resistors. The measured total voltage UM is the standard of the pressure on the diaphragm.GB35132 451 2 3 4 5 p U0 UM R1 R2Diaphragm Silicon chip Reference vacuum Glass base (Pyrex) Bridge circuit Measured pressure Supply voltage Measured voltage Tenacity (pressed) Tenacity (stretched)SP82_5214 52 61.3 2 43 75 6 7Electrical supply lines with glass bushing Reference vacuum Measuring cell (chip) with evaluation electronics Glass base Cap Supply line of the measured pressure pSP82_5312 3456 71 2 3 4 5 6 7Temperature sensor (NTC) Lower part of housing Intake manifold wall Sealing rings Electrical connection (connector) Housing lock Measuring cellSP82_54 Protected by copyright. Copying for private or commercial purposes, in part or in whole, is not permitted unless authorised by ŠKODA AUTO A. S. ŠKODA AUTO A. S. does not guarantee or accept any liability with respect to the correctness of information in this document. Copyright by ŠKODA AUTO A. S.�36GBPressure senderVersion with reference pressure in the hollow space StructureThe silicon chip is located on the glass base and the measured pressure is applied directly to that side, where you will find the evaluation electronics. For this reason, this side is protected by a special gel. The reference vacuum is present in the hollow space between the chip and the glass base. A temperature sensor is often integrated in the housing of the sender which protrudes into the cavity of the flowing air. It reacts very quickly to temperature changes and its signal is evaluated independently.Function principleThe operating principle is identical to the version with the reference vacuum on the structure side. The only difference is that the diaphragm of the measuring cell is deformed in the opposite direction.4 3 1 25 1 2 3 4SP82_555 6 7 6 71 2 3 4 5 6 7 pProtective gel Gel frame Glass base Ceramic hybrid substrate Hollow space with reference vacuum Measuring cell (chip) with evaluation electronics Outputs welded on Measured pressureUsage: Pressure sender in intake manifold and charge pressure sender (250 kPa) This sender measures the absolute pressure in the intake manifold between the charger and the engine in relation to the reference vacuum. This allows the precise air mass to be determined.Protected by copyright. Copying for private or commercial purposes, in part or in whole, is not permitted unless authorised by ŠKODA AUTO A. S. ŠKODA AUTO A. S. does not guarantee or accept any liability with respect to the correctness of information in this document. Copyright by ŠKODA AUTO A. S.�1 2 3 4 5 6 7Intake manifold wall Housing Sealing ring Temperature sensor (NTC) Electrical connection (connector) Housing lock Measuring cellSP82_56Ambient pressure sender (60 - 115 kPa) This sender measures the absolute pressure and is located directly in the control unit or the engine compartment. The signal is used to correct the values, with which the control loops operate, depending on the altitude e.g. exhaust gas recirculation or charge pressure control. Oil pressure sender (50 - 1000 kPa) This sender measures the absolute pressure of the oil and is mounted on the oil filter. The measuring cell is used for measuring the pressure in the low pressure part of the fuel tank. The sender is mounted on the fuel filter, possibly inside it.GB37Pressure senderHigh-pressure senderStructure and function principle The core of the sender consists of a steel diaphragm on which resistors are vacuum-metallised in the bridge circuit. The measuring range of the sender depends on the strength of the diaphragm. The pressure and the strength are directly proportional. The measured pressure acts on the diaphragm, its deflection changes the tension of two resistances. The resulting measuring voltage in the bridge (80 mV) is conducted into the evaluation circuit, which amplifies the signal (5 V) and forwards it to the control unit.12 34 5SP82_571 2 3 4 5Electrical connection (connector) Evaluation circuit Steel diaphragm with vacuum-metallised resistors Pressure port Mounting threadUsage: High-pressure senders are used in motor vehicles for measuring the pressure of the fuel and the brake fluid. Pressure sender for diesel in the pressure vessel (180 MPa) This sender measures the pressure in the distributor pipe (rail) in the Common Rail diesel injection system. The pressure is also controlled by the circuit and is independent of the engine speed. Pressure sender for petrol in the pressure vessel (5 - 15 MPa) This sender measures the pressure in the distributor pipe (rail) of the MED system - Motronic with direct fuel injection. The pressure depends on the speed. Pressure sender for brake fluid (25 - 35 MPa) The sender measures the pressure of the brake fluid in the hydraulic unit of the system to ensure safety.38Protected by copyright. Copying for private or commercial purposes, in part or in whole, is not permitted unless authorised by ŠKODA AUTO A. S. ŠKODA AUTO A. S. does not guarantee or accept any liability with respect to the correctness of information in this document. Copyright by ŠKODA AUTO A. S.�GBFlow meterMeasured properties, measurement principlesIn the vehicle, flow meters are used for measuring the amount of fuel delivered or the intake air volume to be combusted. Measuring the fuel flow was carried out in internal combustion engines without electronic control, e.g. to display the fuel consumption for a given distance. Measurement of the air flow In the chemical process of fuel combustion, the mass ratios of the intake and charge air are taken into account. In petrol engines, the air mass flow is the most important variable for the pollution, whereby the senders which measure the quantity of gas flow are called anemometers. The maximum measured mass flow is in the range of 400-1200 kg/h for engines and the ratio between the minimum and maximum flow at idle is 1:90-1:100 with an accuracy of 1-2% of the measured value. The air flow senders are very curved so that the measured signals have to be linearised prior to evaluation. The flow through the pipeline can be either laminar or turbulent. This depends on the factor of the Reynolds number Re. Re = ν ● E ην - flow velocity D - cross-sectional dimension η - kinematic viscosity of the medium If the value R is greater than 1200, a turbulent flow occurs, which can be assumed for vehicles (ν = constant). If it is lower, there is a laminar flow. The flow can then be calculated as follows: Volume flow: Mass flow:QV = ν ● A QM = ρ ● ν ● Aρ - density of the homogeneous medium Protected by copyright. Copying for private or commercial purposes, in part or in whole, is not permitted A - measurement cross-section unless authorised by ŠKODA AUTO A. S. ŠKODA AUTO A. S. does not guarantee or accept any liability In practice, the measurement is made at the point where there is a narrow cross-section by measuring the mean value of the flow rate: QStr = const ● QV ● QMwith respect to the correctness of information in this document. Copyright by ŠKODA AUTO A. S.�The drop in pressure at the flow meter must not exceed the value of 20-30 mbar.1 2 A Q R r v(r) Laminar flow Turbulent flow Cross-sectional area of the pipe Passage Radius of the pipe Distance from the centre Flow profile2 1SP82_66GB39Flow meterHot-wire air-mass meter HLMStructure and function principle The sender consists of a measuring tube through which flows the intake air. Inside runs a thin filament made of platinum with a diameter of 70 microns and a resistance RH. A resistor Rk for the temperature compensation is present against the direction of flow. The control circuit ensures that the temperature of the wire is higher by a constant difference. The heater current IH generates a voltage UM that is proportional to the air mass flow based on the resistance measurement RM.RK RH RM R1.2 UM IH tl QmSP82_71Resistor for the temperature compensation Resistance filament Measuring resistance Resistors for the bridge balance Measured voltage Heater current Air temperature Air flowUsage: The hot-wire air-mass meter HLM is located between the air purifier and the throttle valve. It measures the intake air mass flow QM through the engine and is the fastest of all flow meters. Hot-wire- / hot-film anemometer If a current IH flows through a thin wire with the electrical resistance R, the wire heats up. If a medium with the density p and the speed υ flows around it, a balance results between the forwarded electric power pel and the pneumatic secondary power pv. Pel = PV IH2 ● R = c1 ● λ ● Δν Here, the thermal conductivity: λ = c2 - heat loss1QLM + c2Then: IH = c1 ●(QLM) + c2 ●Δν RProtected by copyright. Copying for private or commercial purposes, in part or in whole, is not permitted unless authorised by ŠKODA AUTO A. S. ŠKODA AUTO A. S. does not guarantee or accept any liability with respect to the correctness of information in this document. Copyright by ŠKODA AUTO A. S.�3 2SP82_691 2 3 Qlm xBezel Damping system Soft return spring Air mass flow Position of the disc shutter depending on the flowGB40Hot-film air-mass meter HFM2Structure and function principle The temperature of the electrically heated platinum resistance RH is measured by the resistor RS. The heater element and the resistor for the temperature compensation Rg are thermally separated by a slot. All of these resistors are located on a silicon wafer. The operating principle is similar to the sender HLM.RK RH RS R1,2,3 UM IH tL QMSP82_72Sender for temperature compensation Heating resistor Sensor resistor Bridge resistors Measured voltage Heater current Air temperature Air flow3121 2 3 RK RH RS R1SP82_73Ceramic substrate Two waste strips Contacts Sender for temperature compensation Heating resistor Sensor resistor Bridge resistorUsage: On petrol engines, the hot-wire air-mass meter HFM2 is located between the air purifier and theProtected throttle valve. It measures the intake air mass flow QM through the engine with high by copyright. Copying for private or commercial purposes, in part or in whole, is not permitted unless authorised by ŠKODA AUTO A. S. ŠKODA AUTO A. S. does not guarantee or accept any liability accuracy. with respect to the correctness of information in this document. Copyright by ŠKODA AUTO A. S.�41GBFlow meterHot-film air-mass meter HFM5Structure and function principle The air mass meter HFM5 is inserted into the suction pipe line behind the air purifier. The sensor consists of the member (4), around which flows the supplied air from the inlet chamber (8), as well as the evaluation electronics (3). The measuring elements are vacuummetallised on the semiconductor substrate and the evaluation electronics on the ceramic substrate. The measuring channel (6) is shaped in such a way that eddy currents are prevented, thereby improving the stability against pulsating currents. This sender is the only one which detects a return flow.1234 8 5 6 71 2 3 4 5 6 7 8SP82_74Electrical connection (connector) Measuring tube or wall lining of the air purifier Evaluation electronics (hybrid circuit) Measuring element of the sender Sender housing Measuring channel for the partial flow Output of the measured partial flow QM Input of the measured partial flow QMProtected by copyright. Copying for private or commercial purposes, in part or in whole, is not permitted unless authorised by ŠKODA AUTO A. S. ŠKODA AUTO A. S. does not guarantee or accept any liability with respect to the correctness of information in this document. Copyright by ŠKODA AUTO A. S.�42GB1241 2 3 4 5 6 7 M1,2 T1,27 5 3SP82_756ΔTTemperature profile without flow Temperature profile with flow Measuring element of the sender Heating zone Diaphragm of the sender Measuring tube with air-mass meter Intake air flow Measuring points Temperature values in the measuring points M1,2 Temperature differencePrinciple: The resistor located in the middle of the measuring element (3) heats the micro-mechanical diaphragm of the sender (5) and keeps it at a constant temperature. The temperature drops outside of this controlled zone (4). Two resistors at the points M1 and M2 detect the temperature distribution on the diaphragm. In the idle state, the temperatures are the same (1). When the air flows via the measuring element, the temperatures (2) change, whereby on the intake side, the curve is steeper due to the cooling and on the other side, it flows better due to the measuring element that heats the air. The difference in temperatures at the points M1 and M2 is proportional to the resistance at the resistors. The corresponding voltage is finally converted in the control unit to the value of the air mass flow (kg/h) according to the stored characteristics.Protected by copyright. Copying for private or commercial purposes, in part or in whole, is not permitted Usage: unless authorised by ŠKODA AUTO A. S. ŠKODA AUTO A. S. does not guarantee or accept any liability with measurement respect to the correctness of of information in this document. Copyright by ŠKODA AUTO A. total S.� This sender is used for very accurate the partial air flow based on the current that flows through the measuring tube or through the air purifier. Changes in the temperature of the intake air do not affect the measurement accuracy.GB43Gas sensors, concentration meterMeasured properties, measurement principlesThe concentration of the substance indicates the mass ratio of the individual elements or mixtures of other substances. The concentration meter detects only one element, possibly a substance, the others will be ignored. The following variables are measured on vehicles: oxygen content in the exhaust gases carbon monoxide and nitrogen oxide content humidity in air brake systems humidity of the outside air soot concentrations in the exhaust gases on diesel enginesThe humidity generally indicates the water content in a substance. In the case of gaseous substances, it is water vapour. If moist gas is isobarically cooled, it reaches a certain temperature at a certain saturation level. This temperature limit is called the dew point T. Two terms were introduced for measuring the humidity: Absolute humidity It expresses the mass of water contained in the unit volume of airM m χ = mW = MW ● tr tr pW p-pw (v%)mw ms mtr Mw Mtr p pwMass of water Mass of water in the saturated state Mass of dry gas Molar mass of water Average molar mass of dry gas Total pressure of the gas mixture Partial pressure of water vapoursRelative humidity It indicates the ratio between the amount of water vapour in the air and the amount of saturated vapour at the same temperature and pressure. Saturated steam is a state in which the number of molecules leaving the liquid surface is equal to the number of (after liquefaction) returning molecules. In the automotive industry, only resistance and capacitive sensors are used for measuring the humidity.Protected by copyright. Copying for private or commercial purposes, in part or in whole, is not permitted unless authorised by ŠKODA AUTO A. S. ŠKODA AUTO A. S. does not guarantee or accept any liability with respect to the correctness of information in this document. Copyright by ŠKODA AUTO A. S.�44GBCapacitive sensors As the dielectric of the capacitor, a hygroscopic water vapour absorbent layer is used, whereby these vapours pass through one of the electro