LAB SCOPES
HIGH SPEED VOLTMETER

Replaces:
•
•
•
•
Test Light
Digital Voltmeter/Ammeter/Ohmmeter
Frequency Meter
Duty Cycle Meter
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
VOLTAGE OVER TIME
Scopes measure Voltage and Time
 DVOM’s measure average of pulsing
voltage
 Vertical movement - voltage change
over time
 Horizontal movement - Time it takes for
voltage changes to occur.

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

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

Types of Voltage Signals
Direct Voltage (DC)
 Alternating Current (AC)
 Frequency (Hertz)

SINE WAVES
SINE FUNCTION
 CYCLE
 “0” LINE

4 TYPES OF ELECTRICAL
SIGNALS

TYPE ONE - DC
• Direct Current - Straight Line on Scope
• Varying Voltage Signal
– Switched Voltage
– Voltage Sweep
TYPE TWO - AC
VARYING ABOVE AND BELOW 0
VOLTS
 NOT SINUSOIDAL ON AUTOMOTIVE
 IS USUALLY SAW TOOTH SIGNAL

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)
TYPE FOUR - SERIAL DATA
SERIES OF PULSES IN SPECIFIC
ORDER
 LIKE MORSE CODE
 INFO TO SCAN TOOLS
 INFO BETWEEN BCM’S

SIGNAL CHARACTERISTICS

CAN MEASURE THREE
CHARACTERISTICS OF
WAVEFORMS
• AMPLITUDE
• FREQUENCY
• SEQUENCE OF EVENTS
DC SIGNAL FAILURES

MUST KNOW THREE THINGS
• What are the voltage levels for this circuit?
• What voltage changes should take place
while you’re testing the circuit?
• What does the voltage do as the failure
occurs?
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
THE END