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Chapter 4 Remote Interface Reference
Pulse Width Modulation (PWM) Commands
4
•
If you select the
External
modulating source (
PWM:SOUR EXT
command
), the deviation is controlled by the ±5V signal level present
on the rear-panel Modulation In connector. For example, if you have
set the width deviation to 10 µs, then a +5V signal level corresponds
to a 10 µs deviation. Lower external signal levels produce less
deviation, and negative signal levels produce negative deviation.
Note: The operation of the PWM:DEV command is affected by the
FUNC:PULS:HOLD command (see “Pulse Configuration Commands” on
page 192 for further information). The FUNC:PULS:HOLD command
determines whether pulse width (the default) or pulse duty cycle values
are to be held constant as the period is varied. If the width is held, so is
the width deviation. If the duty cycle is held, so is the duty cycle deviation.
If duty cycle and duty cycle deviation are being held, width deviation
values specified with the PWM:DEV command are automatically
converted to the equivalent duty cycle deviation in percent.
PWM:DEViation:DCYCle {<deviation in percent>|MINimum|MAXimum}
PWM:DEViation:DCYCle? [MINimum|MAXimum]
Set the duty cycle deviation in percent (percent of period). This value
represents the peak variation in duty cycle from the duty cycle of the
underlying pulse waveform. For example, if duty cycle is 10% and duty
cycle deviation is 5%, the duty cycle of the modulated waveform will vary
from 5% to 15%. The default is 1 percent. MIN is approximately 0%.
MAX is approximately 100% (limited by the period, minimum pulse
width, and edge time). The :DEV:DCYC? query returns the duty cycle
deviation in percent.
• The duty cycle deviation cannot exceed the current pulse duty cycle.
• The duty cycle deviation is also limited by the minimum pulse width
(Wmin):
Duty Cycle Deviation < Duty Cycle – 100 X Wmin ÷ Period
and
Duty Cycle Deviation <
100 – Duty Cycle – 100 X Wmin ÷ Period
where:
Wmin = 20 ns for period <
10 s.
Wmin = 200 ns for period > 10 s, but <
100 s.
Wmin = 2 µs for period > 100 s, but <
1000 s.
Wmin = 20 µs for period > 1000 s.
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