3.
Use the vertical POSITION control (4) or (7) to position the trace to the central horizontal gratitude
line passes through the points on the waveform between which you want to make the measurement.
4.
Use the Horizontal POSITION control (10) to set the left-most measurement point on a nearly
vertical gratitude line.
5.
Count the number of horizontal gratitude divisions between the Step 4 gratitude line and the second
measurement point. Measure to a tenth of a major division. Note that each minor division on the
central horizontal gratitude line is 0.2 major division.
6.
To determine the time interval between the two measurement point, multiply the number of
horizontal divisions counted is Step 5 by the setting of the TIME/DIV switch. If the X10 MAG (11) is X
10 (x10 magnification), be certain to divide the TIME/DIV switch setting by 10.
Period, Pulse, Width and Duty Cycle
The basic technique described in the preceeding paragraph can be use to determine pulse parameters such
as period, pulse width, duty cycle, etc.
The period of a pulse or any other waveform is the time it takes for one full cycle of the signal. In Figure 2-7,
the distance between points (A) and (C) represent one cycle; the time interval of this distance is the period.
The time scale for the CRT display of figure 2-7 A is 10 ms/div, so the period is 70 milliseconds in this
example.
Pulse width is the distance between points (A) and (B). In our example it is conveniently 1.5 divisions, so the
pulse width is 15 milliseconds. However, 1.5 division is a rather small distance for accurate measurements,
so it is advisable to use a faster sweep speed for this particular measurement. Increasing the sweep speed
to 2 ms/div as in Figure 2-7 gives a large display, allowing more accurate measurement.
If it is seen small with the TIME/DIV switch you may measure X 10 is expanded condition by putting X10
MAG switch to X10 MAG. The duty cycle may be calculated by knowing pulse breadth and cycle.
The distance between points (B) and (C) is then called offtime. This can be measured in the same manner
as pulse width.
When pulse width and period are known, duty cycle can be calculated. Duty cycle is the percentage of the
period (or total of on and off times) represented by the pulse width (on time).
Duty cycle (%) =
PW (100)
=
A -> B (100)
Period
A-> C
Duty cycle of example =
15 ms x 100
= 21,4 %
70 ms
2.3.3 Frequency
Measurement
When a precise determination of frequency is needed, a frequency counter is obviously the first choice. A
counter can be connected to the CH 1 OUTPUT connector (30) for convenience when both scope and
counter are used. However, and oscilloscope alone can be used to measure frequency when a counter is not
available, or modulation and/or noise makes a counter unusable.
Frequency is the reciprocal of period. Period in seconds (s) yields frequency in Hertz (Hz); period in
millisecond (ms) yields frequency in kilohertz (kHz); period in microseconds (µs) yields frequency in
megahertz (MHz). The accuracy of his technique is limited by the timebase calibration accuracy (see Table
of Specifications.)
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