Fluke DDS Function Generator 271, User Manual

Page: 71 / 132

Hop
Running the Sequence
11
11-3
Both the control mode (internal, external or manual/remote) and internal timing (if
selected) are set with the edit cursor in the rightmost field of the top line of the display;
the diagram shows the default setting of 1 s internal interval. Note that each step can be
set to a different length or a different mode; it is therefore possible to mix internally
timed steps with externally triggered or manually initiated steps. The internal timer can
be set from 2 ms to 65 s in 1 ms increments using the rotary control or direct keyboard
entry. See
Timing Considerations below.
With the interval set to 0.002 s (2 ms), further anticlockwise movement of the rotary
control will select
EXTERNAL
then
MANUAL
; alternatively they can be directly
selected from the keyboard by entering
1 ms
or
0 ms
, respectively. In
EXTERNAL
mode the sequence is stepped on at each rising edge of the trigger signal connected to the
front panel
EXT TRIG
socket. In
MANUAL
mode the sequence is stepped on with each
press of the
MAN/SYNC
key or with an appropriate remote command.
A synchronizing signal is provided at the rear panel
TRIG/SWEEP OUT
socket. At the
entry to each step the signal goes low, followed by a rising edge after the frequency and
wave shape have changed for the new step. However, the rising edge will generally occur
before an amplitude or offset change (if specified) has been completed. See
Timing
Considerations below.
Running the Sequence
To run the hop sequence the edit cursor must be positioned in the
HOP
field; alternate
presses of the
DIGIT
keys will then toggle
HOP
between
RUN
and
OFF
. With
HOP:RUN
the edit cursor is suppressed and no editing is possible. Exiting hop, by
pressing
ESCAPE
, automatically sets
HOP:OFF
and returns the generator to the
setting used before hop was selected.
When hop is running the hop display will show the waveform parameters for each step
which is manually stepped or has a duration greater than 500 ms; the display will not
track the changes of shorter steps or externally triggered steps.
Timing Considerations
The time to set up the waveform at each step will depend on the nature of the change.
The approximate timings for each change, from the trigger edge, are as follows:
Frequency only: 0.5 ms. Frequency changes are phase-continuous.
Frequency and wave shape: 3 ms, but longer if the filter is switched as well.
Amplitude and offset: Up to 40 ms.
If the new amplitude setting involves an attenuator change the output is switched off for
45 ms whilst the change is made to prevent any transients appearing at the output.
The synchronizing signal at the rear panel
TRIG/SWEEP OUT
socket is a low-going
pulse whose falling edge occurs at the start of each step; this is about 1 ms after an
external trigger. The rising edge occurs just after the completion of a frequency or wave
shape change, i.e. 0.5 ms or 3 ms later respectively.
For an amplitude and/or offset change the rising edge occurs slightly later but well before
the 40 ms delay needed to guarantee that the change has been completed; however, if the
amplitude change causes the attenuator to be switched the rising edge will occur after the
attenuator has changed and the output has been switched back on.
The set duration of the step is timed from the rising edge of the synchronizing signal at
the
TRIG/SWEEP OUT socket. The minimum step duration of 2 ms can be used for
frequency only changes but the time needed to implement wave shape, amplitude or
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