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chapter covers issues that relate to defining, downloading and managing custom waveforms.
Note: i Series models do not support arbitrary waveform generation.
4.4.1 Standard Waveforms
For most AC applications, a sinusoidal wave shape is used. The sine wave is the standard waveform
provided on all i and iX Series models. This standard sine wave is always available and is the default
waveform at power-on unless overridden. On iX model power sources, two more standard waveforms
are available, square and clipped.
Figure 4-8: Selecting a Waveform
The square wave provides a high frequency content waveform with relative fast rise and fall times.
Due to AC amplifier bandwidth limitations, the frequency content of the standard square wave has
been kept within the amplifier’s capabilities. As the fundamental frequency is increased, the relative
contribution of higher harmonics is reduced.
The clipped sine wave may be used to simulate voltage distortion levels to the unit under test. The
total harmonic distortion level may be programmed in percent using the CLIP THD field directly below
the FUNC entry.
Note that changing source to regenerate the
clipped sine wave’s data points and reload the waveform
e EUT
4.4.2 Creating Custom Waveforms
the distortion level of the clipped waveform forces the AC
register with the newly requested data. This
process requires the output to be dropped briefly. To avoid interrupting the voltage output to the unit
under test, set the clip level needed before closing the output relay and do not change it while th
is under power. You can then toggle between the clipped sine wave and any other waveform in
memory without interrupting the output.
The iX controller supports up to 50 user defined waveforms in addition to the 3 standard waveforms
Custom waveforms cannot be creat
.
ed from the front panel of the iX Series. Rather, they have to be
downloaded through the IEEE-488, LAN or USB interface.
ata points. Each data point can range between –1 and +1
(floating point number). See iX Series programming Manual (P/N 6005-961) for details on
ill not be
Each waveform is defined by 1024 d
downloading waveforms.
Once downloaded, waveforms remain in non-volatile memory and will be visible in the WAVEFORMS
menu for selection. The user can assign a 12-character name to each custom waveform. Avoid using
any of the standard waveform names (SINUSOID, SQUARE or CLIPPED) as these names w
accepted.
Waveforms may be deleted using the IEEE-488, LAN or USB interface as well. Custom waveforms
cannot be deleted from the front panel however to avoid accidental erasure.
California Instruments 80
User Manual Compact i/iX Series
4.4.3 RMS Amplitude Restrictions
The out . If
the AC source is in the 300 V range, the maximu
waveform is used however, the maximum progra
range v a 1.414 crest factor. A
ltage peak error” message is generated.
put of a sine wave may be programmed to the full rms value of the voltage range selected
m programmable rms voltage is 300 Volt. If a custom
mmable rms voltage may be less than the maximum
alue. The voltage range limit is based on the use of a sine wave with
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 “Vo
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
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