Subject PageElectronic Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3Purpose of Electronic Signals. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3AC Voltage Signals. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4Inductive Signals (Induced Voltage) . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4DC Voltage Signals. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5DC Analog Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5DC Analog Sensors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5NTC Sensors. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5PTC Sensor. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6Potentiometers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7DC Digital Voltage Signals. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8Switched B+ (High/Low) Signal. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8Switched B- (High/Low) Signal. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9Modulated Square Wave . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10Frequency. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10Pulse Width . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11Duty Cycle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11DC Digital Sensors. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12Hall Effect Sensors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12Magnetoresistive Sensors. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13Designated Value Signals. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15Coded Ground Signals. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16DC Digital Input/Output Stages. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .17Transistor Final Stage Function. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .17Modulated, Momentary, Constant B- as Input/Output. . . . . . . . .18Momentary/Constant B+ as an Input/Output Signal. . . . . . . . . . .18Constant B-/B+ To Energize a Component. . . . . . . . . . . . . . . . . .19Modulated B-/B+ To Operate A Component. . . . . . . . . . . . . . . . .20Table of ContentsElectronic SignalsInitial Print Date: 12/04 Revision Date: 3/062Electronic SignalsElectronic Signals Model: AllProduction: AllAfter completion of this module you will be able to: Explain the operation of an Inductive Sensor. Understand the difference between analog and digital signals. Know the difference between NTC and PTC type sensors. Explain the operation and use of different types of signals Recognize signal types on the oscilloscope.Purpose of Electronic SignalsElectronic signals move information much like cars move passengers down the highway.It would be difficult to get to work without transportation, and there would be no trans-portation with out signals.Signals allow devices (e.g. sensors or switches) to communicate with control modules(either complicated processors or simple relays) which in turn perform or request(through more signaling) other functions to be carried out.Signals inform the Climate Control of the outside air temp or tell the brake lights the righttime to illuminate.The use of electronic signals goes far beyond the basic application of electron flow tocontrol components, enabling complex information to be passed from one componentto another.The data (input or output) is conveyed through various forms of changing voltages, resis-tances, current or frequency modulation.Signals are divided into TWO main groups: AC type signals DC type signalsMemory-16-12-8-404812160-50 50100 -100-150 150200250300 -200-250-300A MV0 04 408 8012 12016 160-4 -40-8 -80-12 -120-16 -160Cursor1 Cursor2BVmVTRIGGERLEVELHoldscr eenChannelBZoomAmplitudeChannelAAmplitudeChannelBTimevalueStimulatePrint Change End ServicesMultimeter Counter OscilloscopesettingStimulatorsPresetMeaurementsHelpBMW Measuring System Oscilloscope DisplayDC typeMemory-16-12-8-404812160-50 50100 -100-150 150200250300 -200-250-300A MV0 04 408 8012 12016 160-4 -40-8 -80-12 -120-16 -160Cursor1 Cursor2BVmVTRIGGERLEVELHoldscr eenChannelBZoomAmplitudeChannelAAmplitudeChannelBTimevalueStimulatePrint Change End ServicesMultimeter Counter OscilloscopesettingStimulatorsPresetMeaurementsHelpBMW Measuring System Oscilloscope DisplayAC TYPEAC type3Electronic SignalsElectronic Signals4Electronic SignalsAC Voltage SignalsInductive Signals (Induced Voltage)Inductive sensors produce an AC Sine Wave signal. The AC voltage is induced by theshifting of a magnetic field.The sensor consists of an impulse wheel (the moving part)and a coil wound magnetic core (the stationary part).As each tooth of the impulse wheel approaches the sensor tip, the magnetic field of thesensor shifts toward the impulse wheel and induces a voltage pulse in the windings.As the teeth move away from the sensor, the magnetic field shifts back inducing a voltagepulse in the opposite direction.This shifting of the magnetic field produces an alternating current (positive to negative).Control modules which receive this alternating current, count the impulses (shifts frompositive to negative) and interpret the speed of rotation of the impulse wheel.Note: Voltage levels are dependent on sensor design. Not all inductive sensorsproduce 12 volts.ControlModule GroundNegative sideof the circuit.InternalResistorGroundPositive sideof the circuit.ShieldedGround For sensorleads to preventinductance.Input SignalControl Module senses alter-nating current at this point.5Electronic SignalsDC Voltage SignalsFive Types of DC Voltage Signals Are Used: Analog Signals Digital Signals Designated Value Signals Coded Ground Signals Transistor SignalsDC voltage signals are based on either 5 voltsor 12 volts.DC Analog SignalsAnalog signals transmit information through an electrical circuit by regulating or changingthe current or voltage.The voltage of the signal has no fixed value. The value may beanywhere in the operatingrange of the signal.Three sources of analog signals are: NTC Sensors PTC Sensors PotentiometersDC Analog SensorsNTC SensorsNTC (Negative Temperature Coefficient) sensors change resistance based on temperature.As the temperature goes up the resistance goes down. This decrease in resistance caus-es the voltage drop across the sensor to decrease and the input signal voltage at the con-trol module decreases.PrintMultimeterEndOscilloscopesettingChangeCounterServices HelpStimulators PresetmeasurementsBMW Measuring system Oscilloscope displayFreezeImageChannelBZoomStimulateTimevalueAmplitudeChannelBAmplitudeChannelACursor2 Cursor1 Memory8 166 124 82 40 0-2 -4-4 -8-6 -12-8 -16TriggerlevelV 8[V] A[V]ms-2.0 -1.0 0.0 1.0 2.0-1.5 -0.5 0.5 1.51612840-2-8-12-16T12.6vTypical NTC Sensor Signal6Electronic SignalsPTC SensorPTC (Positive Temperature Coefficient) sensors also change resistance based on tem-perature.In a PTC sensor as the temperature goes up theresistance also goes up.The increase in resistance causes the voltage drop across the sensor to increase andthe input voltage signal at the control module increases.When troubleshooting a faulty input display, the input signal must be verified asgood BEFORE the control module is replaced.When checking a NTC Sensor look for these voltages and problems: 0v = no supply voltage or shorted to ground. 2v = sensor is indicating a warm condition for system being measured. 4v = sensor is indicating a cold condition for system being measured. 5v = sensor or wiring harness is open.Remember a PTC type sensor will indicate opposite results on intermediate readings(i.e. 4 volts = warm).Notes: Typical Application of NTC Type sensor: Engine Coolant Temp Sensor Transmission Temp Sensor T-MAP Sensor IHKA interior air temp sensorPotentiometersA Potentiometer produces a gradually changing voltage signal to a control module. Thesignal is infinitely variable within the operating range of the sensor.This varying voltage reflects a mechanical movement or position of the potentiometerwiper arm and its related components.7Electronic SignalsSliding Contact:Resistance increases throughlength of the sliding contact.Potentiometer Wiper Arm:Input signal control, varies the input signal voltage bythe position of the wiper armon the sliding contact.Control Module Groundand internal resistor for thesliding contact circuit.Control Module Groundwith internal resistor for inputsignal circuit.Input Signal:Used by the control module. As the wiperarm travels clockwise (as shown) the volt-age signal to the control module increases.Control Modulewith internal resistor suppliessource voltage for the poten-tiometer (usually 5 volts).Typical Application of Potentiometers: Pedal Position Sensors Throttle Position Sensors (Also Feedback Potentiometers)8Electronic SignalsDC Digital Voltage SignalsDigital Signals transfer information through anelectrical circuit by switching the current on oroff. Unlike analog signals which vary voltage, adigital signal has only two possible states, con-trol voltage or 0 voltage.Two types of Digital Signals:Switched (High/Low) Signals Modulated Square Wave signalsSwitched B+ (High/Low) SignalThis DC voltage signal produces an ON/OFF type input to the control module. The volt-age level will indicate a specific operating condition.B+ source of the input signal.Switch functions as input con-trol with switch position.Open = 0vClosed = B+Input Signal used by the controlmodule sensing the HI/LOWinput.Control Module with internalresistor and ground.Typical Application of Switched B+ Ignition Switch Light Switch Reed Switch Seat Belt Switch Hall Effect Switch (e.g. Brake Light Switch)9Electronic SignalsSwitched B- (High/Low) SignalThis Ground Signal produces an ON/OFF typeinput to the control module. The voltage levelwill indicate a specific operating condition.The only difference between a switched B- anda switched B+ is the voltage in which the sig-nals are switched.Input signal used by the control modulesensing the HI/LOWinput.Control Module with internalresistor and power supply forthe input signal circuit.Switch functions as input control withswitch position.Open = 12v at the control moduleClosed =