Chapter 5, WEB CONTROL PANEL OPERATION
5-31
Voltage span
This control sets the range of input voltages that will be translated into the
specified frequency span.
Filter control
The FM control signal can be filtered by a simple digital low-pass FIR filter
before being applied to the oscillator, which can be useful for eliminating noise
or glitches on the signal. This control adjusts the filter; when set to 0 the filter is
turned off; as the number is increased, increased filtering is applied.
Amplitude group
Enable AM
When checked, this control turns the amplitude modulation on; when cleared, it
turns it off.
ADC1 as source and Ext ref as source
These radio buttons set the source of the signal that is used for amplitude
modulation. When set to ADC1 as source, the signal should be applied to the
rear panel ADC1 input, and the Center voltage and Voltage span controls are
active.
When set to Ext ref as source the control signal should be applied to the
external reference channel REF IN input. Because the reference channel
internally generates a fixed signal amplitude that is used as the control signal for
the amplitude modulation, the Center voltage and Voltage span controls are
inactive.
Modulation depth
This control defines the maximum amplitude change that will be applied to the
oscillator signal. For example, when set to 100%, the change can be from full
signal output to zero; while if set to 50% the amplitude will change by 50% of its
quiescent level.
Center voltage
This control sets the input voltage corresponding to the quiescent oscillator
output amplitude.
Voltage span
This control sets the range of input voltages that will be translated into the set
range of modulation.
Filter control
The AM control signal can be filtered by a simple digital low-pass FIR filter
before being applied to the oscillator, which can be useful for eliminating noise
or glitches on the signal. This control adjusts the filter; when set to 0 the filter is
turned off; as the number is increased, increased filtering is applied.
5.3.15 Oscillator: Amplitude and Frequency Controls
These two controls duplicate the controls on the Main Controls panel.
Amplitude
This control sets the amplitude of the signal at the front panel OSC OUT connector
to any value between 1 µV and 5 V rms.
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