LAB SCOPES

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LAB SCOPES
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HIGH SPEED VOLTMETER

• Replaces
• Test Light
• Digital Voltmeter/Ammeter/Ohmmeter
• Frequency Meter
• Duty Cycle Meter

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Types Of Oscilloscopes

• Analog
• Real Time (Direct Reading of signal)
• No memory
• Digital
• (LCD or Cathode Ray Tube)
• Uses a memory
• Delayed to screen (need high sampling rate)
• Cursor movement

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VOLTAGE OVER TIME

• Scopes measure Voltage and Time
• DVOMs measure average of pulsing voltage
• Vertical movement - voltage change over time
• Horizontal movement - Time it takes for voltage
  changes to occur.

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SCOPE SCREEN

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

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ADJUSTING SCOPE

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

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Types of Voltage Signals

• Direct Voltage (DC)
• Alternating Current (AC)
• Frequency (Hertz)

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SINE WAVES

• SINE FUNCTION
• CYCLE
• 0 LINE

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4 TYPES OF ELECTRICALSIGNALS

• TYPE ONE - DC
• Direct Current - Straight Line on Scope
• Varying Voltage Signal
• Switched Voltage
• Voltage Sweep

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TYPE TWO - AC

• VARYING ABOVE AND BELOW 0 VOLTS
• NOT SINUSOIDAL ON AUTOMOTIVE
• IS USUALLY SAW TOOTH SIGNAL

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TYPE THREE-PULSE TRAIN

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

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TYPE FOUR - SERIAL DATA

• SERIES OF PULSES IN SPECIFIC ORDER
• LIKE MORSE CODE
• INFO TO SCAN TOOLS
• INFO BETWEEN BCMS

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SIGNAL CHARACTERISTICS

• CAN MEASURE THREE CHARACTERISTICS OF WAVEFORMS
• AMPLITUDE
• FREQUENCY
• SEQUENCE OF EVENTS

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DC SIGNAL FAILURES

• MUST KNOW THREE THINGS
• What are the voltage levels for this circuit?
• What voltage changes should take place while
  youre testing the circuit?
• What does the voltage do as the failure occurs?

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ON-TIME VS. OFF-TIME

• ON TIME Is the time that the circuit is
  energized in one cycle.
• Can be either the upper or lower pulse.
• Ground Controlled
• Feed Controlled

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THE END