User Manual AMETEK Programmable Power
RS Series 109
8. To activate your new selection, YOU MUST CYCLE THE POWER so the AC source re-
initializes. If the source is operated over the bus, a IEEE-488 Device Clear or reset
command (*RST) command will have the same effect.
The new wave group will be active after you turn the power to the unit back on.
4.4.5 RMS Amplitude Restrictions
The output of a sine wave may be programmed to the full rms value of the voltage range
selected. If the AC source is in the 300 V range, the maximum programmable rms voltage is 300
Volt. If a custom waveform is used however, the maximum programmable rms voltage may be
less than the maximum range value. The voltage range limit is based on the use of a sine wave
with a 1.414 crest factor. A 300 V rms sine wave has a 424 Volt peak voltage. The AC source
has a maximum peak voltage capability that is determined by the selected voltage range. If the
user selects a custom waveform with a crest factor that is higher than 1.414, the peak voltage
would exceed this maximum if the rms voltage were to be programmed at 300 V rms.
The RS Series power source automatically limits the maximum allowable programmed rms
voltage of a any custom waveform by calculating the crest factor of the selected waveform and
controlling the rms limit accordingly. Thus, each custom waveform may have a different
maximum rms value. The 3Pi controller will prevent the user from programming the rms voltage
above this limit. If a value is entered in the PROGRAM 1 menu above this value, a “Voltage peak
error” message is generated.
Figure 4-31: Waveform Crest Factor Affects Max. rms Voltage
The figure shown here illustrates the relationship between the crest factor of the wave shape (or
its “peakiness”) and the maximum peak voltage allowed for a given voltage range. Since the
peak voltage cannot exceed the AC source’s capabilities, the programmable rms voltage has to
be restricted, in this case to only 167.8785 volt for the waveform on the left. The sine wave on
the right can be programmed to the full 300 V rms as this still falls within the same peak voltage
limitation of the AC source.
If the RS Series is used over the bus, the “:VOLT? MAX” query command can be used to
determine the maximum allowable RMS voltage for the selected waveform. Using the returned
value as part of a program will prevent range errors.
4.4.6 Frequency Response Restrictions
The user may create a waveform that contains any number of harmonic frequencies of the
fundamental. The AC Source itself however has a finite signal bandwidth and will attenuate
higher frequency components of the signal. To limit the maximum frequency component of the
output signal, the 3Pi controller automatically applies a band-pass filter to all custom waveforms
as they are downloaded. The controller implements the following process for user defined
waveforms:
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