LESSON 2
DEFINE THE THEORY AND APPLICATION OF AN OSCILLOSCOPE
TASK
Describe the theory and
terminology related to maintenance procedures for
the
oscilloscope.
CONDITIONS
Given the information and illustrations
about
terms
and
theory
relating
to
application of the oscilloscope.
STANDARDS
Demonstrate competency of the task skills and knowledge by correctly responding to
80 percent of the multiple-choice test covering theory and terminology of using an
oscilloscope.
REFERENCE
None
Learning Event 1:
DESCRIBE THE PRINCIPLES OF OPERATION OF AN OSCILLOSCOPE
1.
The cathode-ray oscilloscope is a test instrument using a cathode-ray tube
(CRT). It is one of the most important units of test equipment in maintenance and
service. It is used to give a visual presentation of circuit waveforms which, by
comparison, show the operation efficiency level of a portion of a circuit or a
complete circuit contained in the system being tested.
2.
When using the oscilloscope, you compare actual waveforms against optimum-
efficiency waveforms which are permanently printed and located either at the
equipment test points or on schematic diagrams in the applicable technical manuals.
Scope patterns periodically taken at the test points are compared with those
printed waveforms. Differences between the optimum waveform and the scope pattern
indicate that the circuit (and the equipment) is below the optimum performance
level and that corrective action should be applied.
3.
The beam of electrons from a cathode-ray tube follows a straight line unless
deflected by an electric or a magnetic field. Cathode-ray tubes are of two types
according to the method used to deflect the electron beam.
These types are
electrostatic and electromagnetic.
The electrostatic type of CRT is used in
practically all cathode-ray oscilloscopes operating at test instruments.
In the
electrostatic type, the beam is deflected by an electric field
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