LAB SCOPES

HIGH SPEED VOLTMETER n Replaces: Test LightTest Light Digital Voltmeter/Ammeter/OhmmeterDigital Voltmeter/Ammeter/Ohmmeter Frequency MeterFrequency Meter Duty Cycle MeterDuty Cycle Meter

Types Of Oscilloscopes n Analog: Real Time (Direct Reading of signal)Real Time (Direct Reading of signal) No memoryNo memory n Digital: (LCD or Cathode Ray Tube)(LCD or Cathode Ray Tube) Uses a memoryUses a memory Delayed to screen (need high sampling rate)Delayed to screen (need high sampling rate) Cursor movementCursor movement

VOLTAGE OVER TIME n Scopes measure Voltage and Time n DVOM’s measure average of pulsing voltage n Vertical movement - voltage change over time n Horizontal movement - Time it takes for voltage changes to occur.

SCOPE SCREEN n Divided into small sections n Grids or Graticules n 10 grid X 10 grid Screen n Voltage level between grids is adjustable n Time base between grids is adjustable

ADJUSTING SCOPE n Largest waveform n 2 or 3 complete cycles n Voltage range with one grid above max. volts and one grid below min. volts. n Trigger Level n Trigger Slope

Types of Voltage Signals n Direct Voltage (DC) n Alternating Current (AC) n Frequency (Hertz)

SINE WAVES n SINE FUNCTION n CYCLE n “0” LINE

4 TYPES OF ELECTRICAL SIGNALS n TYPE ONE - DC Direct Current - Straight Line on ScopeDirect Current - Straight Line on Scope Varying Voltage SignalVarying Voltage Signal –Switched Voltage –Voltage Sweep

TYPE TWO - AC n VARYING ABOVE AND BELOW 0 VOLTS n NOT SINUSOIDAL ON AUTOMOTIVE n IS USUALLY SAW TOOTH SIGNAL

TYPE THREE-PULSE TRAIN n VARIABLE FREQUENCY (pip,maf) Number of cycles that happen in one secondNumber of cycles that happen in one second n VARIABLE DUTY CYCLE measurement comparing signal on-time to the length of one complete cycle (m/c solenoids)measurement comparing signal on-time to the length of one complete cycle (m/c solenoids) n VARIABLE PULSE WIDTH Actual on-time of a signal measured in milliseconds. (fuel injection)Actual on-time of a signal measured in milliseconds. (fuel injection)

TYPE FOUR - SERIAL DATA n SERIES OF PULSES IN SPECIFIC ORDER n LIKE MORSE CODE n INFO TO SCAN TOOLS n INFO BETWEEN BCM’S

SIGNAL CHARACTERISTICS n CAN MEASURE THREE CHARACTERISTICS OF WAVEFORMS AMPLITUDEAMPLITUDE FREQUENCYFREQUENCY SEQUENCE OF EVENTSSEQUENCE OF EVENTS

DC SIGNAL FAILURES n MUST KNOW THREE THINGS What are the voltage levels for this circuit?What are the voltage levels for this circuit? What voltage changes should take place while you’re testing the circuit?What voltage changes should take place while you’re testing the circuit? What does the voltage do as the failure occurs?What does the voltage do as the failure occurs?

ON-TIME VS. OFF-TIME n ON TIME: Is the time that the circuit is energized in one cycle. Can be either the upper or lower pulse.Can be either the upper or lower pulse. Ground ControlledGround Controlled Feed ControlledFeed Controlled

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