Sequoia / Tahoe Series User Manual California Instruments
M447352-01 REV-A 245
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Figure 6-1.HARMONICS Screen, Waveform Information
6.3 RMS Amplitude Restrictions
The maximum RMS value that could be programmed within a voltage range is dependent on the crest
factor of the output voltage waveform due to constraints of the power stage amplifier on producing the
peak voltage. The voltage range limit is based on a sine wave with a crest factor of 1.414: for example, in
the High-Range, the full-scale AC sine wave voltage of 400 V(RMS) has a peak voltage of 566 V(PK), and
that is the maximum peak voltage that could be produced for any other type of waveform. Therefore, if a
custom waveform is used and the crest factor is greater than 1.414, the maximum programmable RMS
voltage would be less than the maximum range value in order to stay within the peak voltage limit.
The power source automatically limits the maximum allowable programmed RMS voltage of any custom
waveform by calculating the crest factor of the selected waveform to ensure that the peak output voltage
capability is not exceeded and controlling the RMS limit accordingly. Therefore, each custom waveform
might have a different maximum RMS value. The power source controller will prevent the user from
programming the RMS voltage above this limit. If a value is entered above this value, a “Voltage peak
error” message is generated.
If the power source is controlled through the remote digital interface, the SCPI query command,
:VOLT? MAX, could be used to determine the maximum allowable RMS voltage for the selected waveform.
The query returned value could be used as part of a program to preclude range errors.
6.4 Frequency Response Restrictions
The user could create a waveform that contains any number of harmonic frequencies of the fundamental.
However, the power source has a finite signal bandwidth and would attenuate frequency components of
the signal that exceed that bandwidth. To limit the high-frequency components of the output signal, the
power source controller automatically applies a band-pass filter to all custom waveforms as they are
downloaded. The power source controller implements the following process for user-defined waveforms:
Each downloaded waveform will have a computed frequency limit that is less than or equal to the maximum
frequency limit of the power source. The frequency limit is a function of the harmonic content of the
waveform and is derived from the following relation:
F
harmonic
≤ (V
full-scale
×
F
maximum)
/ (V
harmonic-amplitude
× harmonic-number),
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