User Manual
2253i / 2253iX
AMETEK
California Instruments
82
4.4.3 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 iX Series power source automatically limits the maximum allowable programmed rms voltage of
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
controller will prevent the user from programming the rms voltage above this limit. If a value is entered
in the PROGRAM menu above this value, a “Voltage peak error” message is generated.
Figure 4-9: 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 iX 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.
4.4.4 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 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:
Each downloaded waveform will have a computed frequency limit that is less than or equal the
maximum frequency limit of the AC source. The frequency limit is a function of the harmonics content
of the waveform and will follow the equation below.
Fmax
h
= Fmax/(level * h
n
)
Where:
