Function generator description of DEWESoft 6.3
DEWESoft 6.3 includes full-featured signal generator with 16 or more signal
outputs.
Available modes are fixed frequency, sweep, burst or stepped sweep. There are
many functions available for each mode like frequency, operation mode, timings,
control and so on. For each channel individually we can decide on waveform type
(sine, triangular, rectangular, saw, white noise or trigger). Amplitude, offset and
phase can be defined for each channel as well.
The start and stop of generation can be with a half sine window, so the
amplitude will not rise from 0 to full amplitude immediately, but within a certain
time which ensures that the systems under test don’t suffer from impact shock.
Let’s look at all operation modes of the signal generator.
FIXED FREQUENCY
Fixed frequency offers to output the selected signals at fixed output rate. Output
frequency is the same for all the channels and is defined in the setup.
But fixed frequency does not necessarily mean that it is really fixed, but we can
choose to have control of it during the signal generation.
Not only that - the setup of all the basic parameters can be done also while
outputting the data with manual control dials to change the frequency on all
channels as well as amplitude, offset and phase angle of the single channel as
shown in the next picture.
It is crucial that changes during the output happen without a single glitch in the
signal with predefined speed. In the top left dial we can see the red point that
shows current frequency and the grey circle with wanted frequency. The
frequency will change with predefined speed and slowly red point (current
frequency) merges with grey point (wanted frequency). On the oscilloscope
below we can see that the signals does not have any distortion or glitches
because of changing the signals. Frequencies can be adjusted with 0.1 mHz
resolution.
All generated channels themselves are available as DEWESoft virtual channels.
Also amplitudes, offsets and phase angles are available as channels so they can
be put in any visual control to monitor the frequency generator or they can be
used in math channel for simulation or control purposes. On the picture below we
can see how the phase angle for the generated channels has been adjusted.
Such function generator is valuable in laboratory testing of electronic circuits,
power amplifiers, filters and so on. Also it provides a great base for calibration
procedures. Multiple channels ensures a great chance to test delays and phase
errors.
SWEEP
Second operation mode is the sweep. Start, end frequency and sweep time are
defined in the setup before generation. In addition to this sweep can be either
linear or logarithmic to provide more cycles at lower frequencies.
Sweeps are useful for testing electronic circuits like filters as well as in
automated modal analysis.
BURST MODE
For burst mode the rise, fall and dead time is defined. Bursts are useful in testing
response characteristics of the systems.
Within the burst we can choose to have any signal, but in practice noise is
usually used as the base generated signal. Bursts are usually enhancements of
the noise excitation for measuring transfer function. With burst we eliminate the
need of using the window of frequency analysis and therefore eliminate the
errors caused by window.
STEPPED SINE
Stepped sine is very special procedure for modal testing where the signal
remains at certain fixed frequency to allow the structure to settle to that
frequency. In addition to this more exact frequency resolution of transfer
function can be achieved with smaller steps. Even though this procedure is the
slowest to finish the test, it provides most accurate results.
In the recorder in the middle the frequency steps can be seen, one channel is
defined as the trigger channel and this one can trigger the acquisition system to
take results of modal test.
The start and stop of generation can be either on start of acquisition or manual.
Each operation mode carries different manual control:
- at fixed frequency the generation can be started and stopped(as seen on
the picture below);
- at burst mode the individual bursts are issued with manual control;- at stepped sweep we can go manual to the next frequency.
DEWESoft provides DCOM control interface to data, acquisition and data analysis.
With the new version these functions expands to function generator to control all
the modes and parameters. This functionality provides a great chance to make
automated procedures for testing and calibration.