LESSON 3.
MODEL 5345A THEORY OF OPERATION
ACCP Subcourse MM0462
Model
5345A
Time
Measurement System
LESSON OBJECTIVE
Given supportive text and diagrams:
1.
Explain the purpose
of
each
major counter circuit.
2.
Trace signal flow
for
each
measurement function.
3.
Perform theoretical trouble-
shooting to circuit level.
CREDIT HOURS
Three
TEXT
Your duties as a calibration specialist will probably dictate that you
troubleshoot and repair an electronic counter. Most counters have related
theories of operation, and although the adage that "if you know one you know
them all" is not entirely true, your knowledge of the circuitry of the Model
5345A will undoubtedly be an advantage in repair tasks. The majority of the
Model 5345A circuitry is comprised of common logic elements: AND gates, D-
Type flip-flops, JKs, etc. Examining signal processing within the chips is
more pertinent to an engineer than to a calibration specialist. You need to
understand signal flow and logic states within the counter, and this lesson
is devoted to that end.
1.
LOGIC ELEMENTS.
Two states exist in the binary system, 1 and 0. HIGH (H) and LOW (L)
are used to represent the levels of 1 and 0.
HIGH always represents the
more positive level, whether it be positive or negative logic, Figure 1
shows four pairs of logic symbols that have the same truth tables and can be
used interchangeably. The same function is performed by what appears to be
two different logic symbols.
Figure 1A illustrates the OR functions and, as shown by the truth
table, a HIGH output can be obtained from any combination of input logic
levels. The only condition which will not yield a HIGH output is when both
the A and B inputs are LOW. The AND function is shown in figure 1B. A HIGH
state at the Z output will only be present when both the A and B
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