BNC 645 - Manual (Page 52)

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FREQuency {<frequency>|MINimum|MAXimum}
VOLTage {<amplitude>|MINimum|MAXimum }
VOLTage:OFFSet {<offset>|MINimum|MAXimum }
FSKey: FREQuency {<frequency>|MINimum|MAXimum}
FSKey:INTernal:RATe {<rate in Hz>|MINimum|MAXimum }
FSKey:SOURce {INTernal|EXTernal}
FSKey:STATe ON
4.11 PWM Waveform
Model 645 waveform generator provides the capability to output a pulse
width modulation (PWM) for pulse carrier waveforms. In PWM, the pulse
width of the pulse carrier waveform varies with the modulating waveform.
The pulse width can be expressed either in time units or duty cycle (i.e.,
percentage of the period).
Carrier Waveform
Pulse waveform is the only waveform that is available for PWM. The
default period for the carrier pulse is 1 ms, and the range is from 100 ns
to 2000 s.
Modulating waveform
Model 645 accepts either internal or external modulating source but not
both at the same time. The default source is internal, and the default
internal modulating waveform is sine wave. For internal source, one may
also choose from square with 50% duty cycle, URamp (Up or Positive
ramp with 100% symmetry), DRamp (Down or Negative ramp with 0%
symmetry), triangle (ramp with 50% symmetry), noise and arbitrary
waveforms. If an arbitrary waveform is chosen, the number of points in
the waveform is limited to 4k points with an automatic decimation
process. The default frequency for internal modulating waveform is 10Hz,
and the acceptable range is from 2 mHz to 20 kHz.
When an external source is selected, the carrier waveform is modulated
with an external waveform coming from the Modulation In connector on
the rear panel.