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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
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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 ELECTRICALSIGNALS • 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