This is a "how-to"
analog dual-trace lab scope training manual covering the procedures
to set-up and operate an analog dual-trace lab scope to troubleshoot
the circuits of automotive electrical, automotive electronic
and truck electrical and truck electronic circuits. This is also
a great first manual for technicians to learn lab scope terminology
and how to use a dual trace lab scope in auto electronics
and truck electronics repair.
Although this lab scope manual
is based on an analog lab scope rather than a DSO (Digital -
Storage - Oscilloscope) it has a lot of value explaining lab
scopes controls, terminology and wave form analysis to help you to understand your DSO. Eight Chapters
cover aspects of using an analog lab scope with emphasis
on how to analyze circuit wave forms produced by a lab scope.
Lab scopes have been
used in the electronics industry since the 1920's and now are
finding new applications in auto electrical troubleshooting,
auto electrical repair, auto electronic repair and driveability
diagnosis. A lab scope is the ultimate troubleshooting
tool for vehicle electrical repair and vehicle electronic repair.
Once you learn to use a lab scope and realize its benefits you
will wonder how you ever got along without one.
Detailed explanations on lab scope
terminology, function of front panel controls and how to set-up
an analog dual trace lab scope to perform a variety of critical
auto and truck circuit measurements.
Learn techniques for DC
voltage measurement and checking amplitude of electrical noise present; AC voltage
measurement to determine amplitude andfrequency; measuring digital signals for amplitude, frequency and distortion including duty cycle
wave forms as shown below.
Learn to measure AC waveforms for amplitude, frequency and reference to ground.
Learn to measure digital waveforms for amplitude, frequency, reference to ground, pulse width or time duration.
Section 7 is devoted to practice in analyzing wave
forms and detecting when a misadjusted lab scope control may
be the reason a wave form appears incorrect on the CRT but is
correct in the circuit.
In the illustration to the left is a PWM (Pulse-Width-Modulated) wave form which has a fixed base frequency or time PERIOD. The PWM signal changes it's high (HI = B+) and low (LO = B-) time duration.
Start by looking at the top wave form then the next lower until you reach the bottom. Notice the HI time duration increases as the LO time duration decreases.
Next look at the bottom wave form and then the next higher until you reach the top. See the HI time duration decreases as the LO time increases.
That's how PWM wave form controls circuits. It's called Duty Cycle. You can see the changes in a PWM's duty cycle as it happens with a lab scope.
has been added to the scope manual covering current ramping techniques.
An updated 2017 version is now available with minor
revisions and updates on duty cycle.
A wave form record sheet
is provided so that you can build your own wave form record library
covering the vehicles you work on the most. Even if you are using
a digital lab scope exclusively, you will find helpful information
in understanding lab scope terminology and wave