Frequency Measurement - Goldstar OS-7020 Service Manual

6-3 Frequency measurement
The first method; Calculate the one cycle time(interval)
of the input signal and obtain the frequency by equation(4)
Frequency(Hz) =
l (C)
-------- (4)
PERIOD(S)
The second method; Count the repetition number N per
10 divisions in the viewing area, and calculate the frequency
by Equation
(5)
N(C)
( 5 }
Frequency(Hz) =
-
TIME/DIV setting value(s/div)xl0(div}
. When N is large(30-50), the second method can give a high
accuracy level than that obtained with the first method.
This accuracy is approximately equal to the rated accuracy
of sweep rate. However, when N is small, the count below
decimal point becomes very ambiguous, which results in
considerable error.
For the measurement of comparatively low frequencies having
a simple pattern such as sine wave, square wave, triangle
wave, and sawtooth wave, measurement with high.accuracy can
be effected by the following method; Operate the oscilloscope
as an X-Y scope, make the Lissajou's pattern by applying the
signal of which frequency is known, and read the necessary
value.
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N:34.5
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Fig 6-4. Frequency measurement
14