3156B User Manual
Racal Instrument © 2005
Using the Instrument 3-19
Generating
Standard
Waveforms
Standard waveforms are built into the instrument’s program. Nine
standard function shapes are available: Sine, Triangle, Square, Pulse,
Ramp, Sinc and Exponential decaying pulses, Gaussian pulse, and
dc. Every time a standard function is selected the coordinates for this
function are re-computed and placed in the waveform memory.
Therefore, there is a minimal delay from when you select the function
until the output starts generating the waveform. Use the following
function call to select the waveform shape:
ri3156B_set_standard_waveform ()
The function variables are from 0 to 8. Upon power up, the 3156B
defaults to 0 (sine waveform).
0 selects sine waveform
1 selects
triangle
waveform
2 selects
square
waveform
3 selects
pulse
waveform
4 selects ramp waveform
5 selects sinc waveform
6 selects
exponential
waveform
7 selects
gaussian
waveform
8 selects
dc
waveform
After you select the required waveform type and shape, you can
proceed with modifying the waveform parameters. The function calls
that are available for programming standard waveform parameters are
summarized in Chapter 5.
Note
The number of points used to define each Standard
Waveform varies according to the programmed frequency
and therefore, some parameters may not have any effect
on the waveform because too few points are available to
generate the waveform mutation.
As was stated in the note above, the number of points may vary
depending on the output frequency. The reason for this variation is
that even standard waveforms are built from waveform coordinates,
similar to arbitrary waveforms except the standard waveforms are
stored in a special library for immediate use without the need to
compute or download such waveforms. At low frequencies, the
number of points for each standard waveform is 1000 so waveform
modification is possible to within 1/1000 increments. For example, if
you want to modify the duty cycle of a square waveform, your best
resolution is 0.001%.
