Figure 3-37: Waveform Crest Factor Affects Max. Rms Voltage - Ametek CSW5550 User Manual

User Manual
5. Move the cursor to the MORE field at the end of this menu and press the ENTER key. You
are now in the INITIAL SETUP 3 menu.
6. Move the cursor to the WAVE GROUP = field. You can now use the knob or the 0 through 3
key on the front panel to select a different waveform group.
7. Press ENTER to confirm your new selection.
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.
3.13.5 RMS Amplitude Restrictions
The output of a sinewave may be programmed to the full rms value of the voltage range
selected. If the source is in the 312 V range, the maximum programmable rms voltage is 312
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 312 V rms sine wave has a 441 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 312 V rms.
The CSW Series 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 CSW 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.
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 312 V rms as this still falls within the same peak voltage
limitation of the AC source.
If the CSW Series is used through the bus, the :VOLT? MAX query 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.
CSW Series

Figure 3-37: Waveform crest factor affects max. rms voltage

California Instruments
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