2 Oscilloscope'sAn oscilloscope can be a priceless price of test equipment used for observation of electrical/electronic wave patterns.
3 Oscilloscope'sTo properly use an oscilloscope you must understand the scale selections.Must automotive oscilloscope will automatically adjust to the proper scale.It’s the technician job to interpret the reading and determine if the wave form is normal or defective.Not all devices operate in the same manner please check manufactures specifications before replacing any sensor.
4 Oscilloscope'sOscilloscope are used to measure voltage over a period of time.An event that happens over a period of time is called frequency and in measured in Hertz per second.2015105VOLTAGE1 Second ScaleTIME
5 Grid lines 15 10 12.2 filter DC voltage V 5 O L T A G 12.2 filter DC voltageVOLTAGE6 – 9 volts unfiltered DC voltage4 Volts Peak to Peak AC Voltage1 Second scale
6 Oscilloscope's Filtered voltage: A smooth supply of voltage. Unfiltered voltage: Normally a ripple type wave pattern.
7 Oscilloscope'sAn AC wave form change direction from positive to negative.Peak voltage: is the voltage from the highest positive voltage to the lowest negative voltage reading.+5-5
8 Peak to Peak voltage is determine by multiplying: Grid division x voltage setting = Peak to peak voltage
9 Oscilloscope'sOscilloscope can be used to measure an event over a period of time.Frequency: Number of complete cycles per second measured in hertz (Hz).Hertz (Hz): Unit of measurement for frequency. 1 hertz equal 1 cycle per second.
10 Oscilloscope's To check frequency you may need some math. Number of grid lines covered for 1 cycle divided by the time scale.
11 Wheel speed sensorThe Anti-lock Braking System (ABS) relies upon information coming in from speed sensors.The wave form produced is used by the ABS control module to determine if wheel lock-up is occurring.
12 Two ABS wave forms. Both are good the difference is the meter set-up
14 2VOLTSCA LE10 mS2 Volts10 mS Time ScaleNormal ABS Pattern
15 Throttle Position Sensor A throttle position is normally produces an analog signal.The throttle position is normally used to tell the PCM the position of the throttleAnalog signal: an electrical signal that varies in strength.
16 Normal Throttle Position Wave Form Throttle Held openThrottle Snapped54321200 mS Time DivisionNormal Throttle Position Wave FormMost throttle position can be easily seen on the 200 mS scale
17 Defective TPS54321200 mS Time DivisionNormal Throttle Position Wave FormMost throttle position can be easily seen on the 200 mS scale
18 Air Flow MetersThe voltage output from the internal track of an Air Flow Meter (AFM) should be linear to flap movement,This can be measured on an oscilloscope
19 MASS AIR FLOW METERThe waveform should show approximately 1.0 volt when the engine is at idle,Voltage will rise as engine when engine speed is increased.A peak voltage of around 4.5 is normal due to natural inertia.Voltage will drop and then level off
20 Normal float back to match air flow Spike due to accelerationThrottle ReleasedNormal fall-off caused by inertiaAround 1 Volt at idle
21 Hot Wire Air flow Meters Temperature stabilizesVoltage spike due to quick throttle opening54321Throttle ReleasedCold air cooling of wireAt idle around 1 volt normal250 mS time division
22 A defective Mass Air Flow will have low voltage or operate erratic at all throttle angles. A mass air flow angle should change in relation to throttle angle.54321250 mS time division
23 Wave Forms Another common type wave form is the square wave. Most electronic components are controlled by a computer PCM, BCM, ECM, ECU or a host of other names.When the computer turns on a component it usually completes a ground circuit sometime controlling a relay.
24 Square Wave Normal voltage spikes 15 10 5 Normal Square wave. Normal Square wave.NOTE: Any wave that is on more than off or off ore than on is called a pulsed wave.
25 Pulsed WavePulsed waves are used to control several electrical components such as:Fuel pumpCanister solenoidsEGR solenoidsWave length: The time required for on complete cycle of a waveform.
26 Pulsed Wave.The difference in wave length is caused by circuit demands2015105Wave lengthNORMAL PULSE WAVE
27 Pulsed Wave . Voltage did not drop properly 20 15 10 5 Bad pulse wave Bad pulse waveVoltage did increase properly
28 Coolant Temperature Sensor (CTS) Most coolant sensors are Negative Temperature Coefficient (NTC) devices.The sensor resistance starts out high around 200 Ohms and drops as engine temperature increases.
29 Bad CTS wave form Good CTS waveform V O L T S 5 4 3 2 1 50 second scale
30 Bad CTS wave formsBad CTS sensor or electrical connection disconnected waveformVOLTS54321Bad CTS erratic voltage pattern50 second scale
31 Crankshaft SensorThis signal should be test when the engine fail to start due to lack ignition.The crankshaft sensor produces an AC voltage that is low while cranking and increases after the engine starts.AC voltage output is critical, low output can prevent an engine from starting.Even if the signal pattern look good.
32 Crankshaft Sensor Normal due to missing tooth on reluctor or flywheel. The missing tooth is used by the PCM to determine crankshaft position
33 Crankshaft Sensor Voltage at start-up Voltage at higher cranking RPM NOTE: Operating parameters vary from manufactures
34 Crankshaft SensorEngine Running: Note the higher voltage
35 Crankshaft SensorA defective crankshaft sensor will show little or no output on the oscilloscopeProper output voltage is critical.184.108.40.206.2Defective Crankshaft sensorVoltage to LOW
36 Knock Sensor A knock sensor is used with some management systems, The Knock sensor is a small piezo-electrical device. That produces electricity when vibrated.Knock sensor are used to reduce ignition timing when a spark knock occurs. Usually no more than 10˚Knock Sensor
37 Knock Sensor Point where knock occurred 5 V 4 O 3 L 2 T 1 A G E Point where knock occurredVOLTA G ENOTE: Knock sensor output should normally be zero50 mS scale
39 Oscilloscope'sIts important to remember that all electrical wiring will have some type electrical pattern that can be view on an oscilloscope.Open CircuitNOTE: Voltage is “0” on an open circuitGood ground circuit
40 Oscilloscope's Quiz Pattern B Pattern A 1. Technician A says pattern A is DC voltage. Technician B says Pattern B is DC voltage. Who is correct.A. Technician A onlyB. Technician B onlyC. Both A and BD. Neither A nor BPattern APattern B
41 Oscilloscope's Quiz 2. How many seconds pass from point A to Pont B? 4. 4AB1 Second Scale
42 Oscilloscope's Quiz3. Technician A says this pattern is an AC wave form. Technician B says this is DC unfiltered. Who is correct?A. Technician A OnlyB. Technician B onlyC. Both A and BD. Neither A nor B2121
43 Oscilloscope's Quiz 4. What is peak Negative voltage in this pattern? A. - 1 voltB. - 2 voltsC. - 4 voltsD volts21
44 Oscilloscope's Quiz 5. What is peak to peak voltage in this pattern? A. 1 voltB. 2 voltsC. 4 voltsD volts21
45 Oscilloscope's Quiz6. The number of complete cycles per second measured is:A. AmperageB. FrequencyC. OhmsD. Voltage
46 Oscilloscope's Quiz7. Technician A says voltage is measured from point A - B. Technician B says Time is measure from point C-D. Who is correct?A. Technician A onlyB. Technician B onlyC. Both A and BD. Neither A nor BABC D
47 Oscilloscope's Quiz 8. What time scale is this oscilloscope set for? A. 2 mSB. 5 mSC. 10 mSD. 100 mS
48 Oscilloscope's Quiz9. Technician A says the wave form is of a defective TPS (Throttle position sensor) Technician B says the pattern is of a good CTS sensor. Who is correct?A. Technician A onlyB. Technician B onlyC. Both A and BD. Neither A nor B5432150 Second Scale
49 Oscilloscope's Quiz 10. Which diagram is of a good ground circuit? B. 2C. 3D. 41234