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Lab Scopes—just mention the words, and some guys shudder with fear and confusion. Oh, they may not show it, but deep down inside, they get nervous. How do they work, how do you get the pattern on the screen, and what does the pattern mean? How do you know if the signal is good or bad? That’s what this book is about.
The purpose of this book is to make it simple. You'll learn what you need to know to start successfully using a lab scope including:
- How does a lab scope work? (in very simple terms)
- When you look at a pattern on the scope, what are you seeing, and how do you know if it is bad?
- How do you get a pattern on the scope, how do you do the adjustments to make the pattern look right?
- What do you do when you can’t get a pattern on the screen at all? (A lot of guys have this problem, but don’t admit it to their friends…)
- What are some of the different things you can do and see with the lab scope? (Most technicians don’t know how much diagnosis you can do with an inexpensive scope, and a few attachments.)
- What are the different types of scopes? And what are they good for? Do you have to spend a lot of money for a really expensive one? And where would you get one?
- Where and how do you hook up the scope to the circuit? Does it make much difference?
This book consists of 62-pages and is written in a down-to-earth manner so you can quickly learn what you need to know.
About the author:
Steve McAfee is a respected automotive instructor at Skyline College in San Bruno California. He has over 35 years of experience in the automotive field, writes questions for the Smog Check Technician's License exam, and is a California certified clean air car instructor.
Table of Contents
Introduction
Chapter 1 Lab Scopes – How do they work?
Compared to a Scan Tool
Compared to a Voltmeter
What a Lab Scope Shows
Analog or Digital
Analog Lab Scopes
Digital Lab Scopes
Downside of Digital
Advantages of Digital
Introduction to a Basic Model
Divisions or Graticules
Voltage
Time
Zero Point
Channels
Chapter 2 Basic Electricity, Circuits and Digital Signals
What is Electricity?
Definitions
Voltage
Amperage
Resistance
Watts
Types of Circuits
Series Circuit
Parallel Circuit
Digital Signals
Hertz or HZ
Duty Cycle
Pulse Width
Number Symbols
Milli or m
Kilo or K
Micro or m
Mega or M
Chapter 3 Pattern Recognition
Magnetic Pickup RPM Sensor
Hall Effect RPM Sensor
Optical RPM Sensor
Throttle Position Sensor
Fuel Injector
Duty Cycle
Ignition Primary
Alternator Ripple
Chapter 4 Getting a Pattern on the Scope
What if nothing happens when you turn it on?
Where to connect the test leads?
The Black Test Lead
The Red Test Lead
Warning
To look at a Computer Input
About Shielded Wires and Electrical Noise
To look at a Computer Output
How to Connect to the Wire
How to Back Probe a Wire
To Puncture or not to Puncture the Wire
Why Do It? (Puncture Wires)
How to Puncture the Wire
What to Adjust? Or Why Doesn’t My Pattern Look Right?
Voltage Adjustment
Time Settings
Ground Positioning
10:1 Probes
Sampling Rate
What to Do
Chapter 5 Trigger
Positive and Negative Slope
To Adjust the Trigger
Tricky Stuff About Trigger
What Do You Mean Trigger Mode?
Trigger Mode and Intermittent Signals
Uses for Trigger Mode
Chapter 6 Relative Compression
Counter Electro-motive Force
To Measure Starter Current
High Amp Probe (or Current Clamp)
Set Up Your Scope
How Do You Know Which Cylinder is Low?
Relative Compression Test
Chapter 7 Fuel Pumps
Low Amp Probes
Where to Attach the Current Probe
About Fuel Pumps
Fuel Pump Commutator Segments
Fuel Pump Brushes
Another Fuel Pump Design
Good Fuel Pump Pattern
Bad Fuel Pump Pattern
After Replacing the Pump
Chapter 8 Primary Ignition
How to Generate Spark
Capacitive Discharge System
Primary Wiring
10:1 Filter
When You Hook Up Your Scope
What The Scope Pattern Means
Dwell or Saturation
Spark Duration
Using Spark Duration for Diagnosis
High Resistance
Low Resistance
RPM Probes
RPM Trigger
Primary Ignition Pattern
High Resistance Problem
Chapter 9 Primary Ignition Amperage or Current Ramping
Counter Electromotive Force (CEMF)
Primary Ignition Volts
Primary Amperage
Computer Controlled Dwell
Low Current Probe
What To Look For
Normal Good Current Ramp
Possible Problems to Diagnose
Chapter 10 Secondary Ignition
High Voltage
Basic Secondary Ignition Pattern
Firing KV
String Theory
Open Spark Plug Wire
High KV
High Resistance Problems
Low KV
Low Resistance Problems
String Theory Example
Low Resistance
10,000:1 Probe
Secondary Ignition Readings
Secondary Hookup
Voltage Between Probe and Ground
Using an Adapter
Using Adapters to Pick Up Signals
Foil Tape
“Right Side Up” Patterns
Pattern Points Down
Ignition Sparks Go Down
DIS Systems
Parade Patterns
Normal Engine
Low Resistance Problem
Parade Pattern of 4 Cylinder Engine
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