Global Specialties 4005 - Manual - Manual (Page 17)

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b. Adjust the longer duration portion of the waveform (rest time for pulses, rise time for ramp
waves) with the SYMMETRY control.
D. If a specific pulse width (specific fall time for ramp wave) is not critical, but a specific repetition
rate is required, the desired waveform may be obtained as follows:
a. Observe the oscilloscope and adjust the SYMMETRY control to obtain the approximate
desired pulse width vs. rest time ratio (rise time vs. fall time ratio for ramp waves).
b. Adjust the repetition rate with the frequency controls FREQ. dial and RANGE switch. The
frequency controls affect both the pulse width and repetition rate.
2) Considerations
A. When generating ramp waves or skewed sine waves, it may be easier to measure the time
periods on oscilloscope using the square wave mode, then switch to the desired operating
mode.
B. For ease and accuracy in measurement, use a higher sweep speed on the oscilloscope to
expand the pulse width for measurement, and then reduce the sweep speed to measure the
repetition rate.
C. Repetition rate may be expressed as a frequency or time period. Measure the repetition rate
as a time period on oscilloscope and convert to frequency if required. The repetition rate
includes the full cycle, both the pulse width and rest time for pulses, the rise time and fall time
for ramp waves.
D. Repetition rate can be measured accurately and easily as a frequency or time period with a
frequency counter.
E. Pulse width also can be measured on a frequency counter, but only with the SYMMETRY
control set off before the pulse waveform is “stretched”. Pulse width equals one-half the time
period of the square wave. If the counter is not equipped for period measurement, calculate the
frequency, which is equivalent to the desired pulse width, and measure the frequency of the
waveform.
1
DESIRED PULSE WIDTH x 2
DESIRED FREQUENCY =