Sweep Mode (Sweep); Burst Mode (Burst); Fig. 5.7: Hmf2 Settings; Fig. 5.8: Burst Example - Hameg HMF2525 Handbuch

E x t e n d e d o p e r a t i n g m o d e s
A convenient way to view the output signal of this measurement
application is to connect an oscilloscope to the SIGNAL
OUTPUT connector of HMF2 via a BNC cable. Activate the
signal output of the HMF2 and press the AutoSet button of the
osciloscope (if available) to view the modulation result.
To sum up:
The bottom line of this little experiment is that you can alter a
modulation on two different ways - first by changing the ampli-
tude at the modulation source (HMF1) and second by changing
the duty cycle / deviation levels at the modulator (HMF2).
5.2

Sweep mode (SWEEP)

In the sweep mode the Start
creased in steps within a given sweep time (Time) up to a
preset Stop frequency. In case the stop frequency was
chosen higher than the start frequency the sweep will run from
the higher to the lower frequency. The Center frequency
and the Span frequency are directly related to the start
and stop frequencies.
Additionally, linear or exponential sweep can be chosen (Spa-
cing). The socalled Marker frequency must be set
between the start and stop frequency. If the signal frequency
reaches the marker frequency a signal will be generated avai-
lable at the TRIG OUTPUT connector.
The sweep function can not be combined with the gating
function.
The sweep mode is selected by pushing the SWEEP key
which will light up. The parameters Time, Start and Stop
frequency can be set independently. The Time is selec-
table from 1ms to 500s.
The sweep parameters are set via the numerical keyboard or the
knob. Setting or changing of parameters are also possible during
a sweep, any changes will be immediately apparent. The sweep
actually running will be terminated and a new one started; the
display will show the parameters activated.
The sweep function will be left by pushing the SWEEP key
again.
5.2.1 Submenu TRIGGER
The sweep signal may also be triggered, this can be selected
with the soft keys. In trigger mode the HMF2525 / HMF2550 will
generate the start frequency and wait for the trigger in order to
start a sweep. The sweep will run with the parameters selected
and stop, waiting for the next trigger.
42
Subject to change without notice

Fig. 5.7: HMF2 settings

frequency will be in-
5
In the Trigger submenu the trigger source (Imm. / Ext.),
the connector TRIG OUTPUT (On/Off) as well as the
associated edge settings (Rise / Fall) can be defined. The
trigger source can be set to intern (Imm./ immediately) or
extern. In the mode Ext. 3 different trigger options exists.
The instrument selects / performs the appropriate function
automatically:
– by pressing the blue REM/TRIG button a manual trigger
is initiating without an external signal source is needed,
– sending the remote command TRIG via interface,
– depending on the chosen setting a positive / negative TTL
signal is generated on the front panel connectors TRIG
INPUT / OUTPUT.
5.3

BURST mode (BURST)

The BURST mode is available for each waveform, also for any
symmetry setting. If this mode is chosen the white LED of the
BURST key will light up. In BURST mode these selections are
available:
– continously
– triggered (manual/Remote/external)
– gated (GATED externally synchronous or asynchronous)

Fig. 5.8: BURST example

In the triggered BURST mode a trigger will generate a burst
with a predefined number of cycles. Such a n-cycle burst begins
and ends at the same point of the signal which is called start
phase. A start phase 0º equals the beginning and 360º the end
of the waveform defined. If the burst counter was set to infinity,
a continuous waveform will be generated upon a trigger. The
trigger source may be an external signal, an internal clock
signal, a manually initiated trigger (REM/TRIG button
„triggered"-mode), resp. the corresponding remote command
(TRIG). The trigger input for an external signal is the TRIG
connector on the front panel. The logic signal applied
17
INPUT
is referenced to the instrument case which is ground potential.
In gated BURST mode (GATED), the signal will be either on or
off, depending on the level of the external signal at the „Trigger
input/ouput" connector. If the gate signal is „true" (high +5V),
the function generator will deliver a continuous signal until
the „gate" closes (0V TTL low). If no power is applied to the
TRIG INPUT connector, the output signal will stop as the
function generator will stop generation. The output level will
correspond to the start level of the waveform selected. In the
asynchronous GATED mode the phase of the gated signal is cut,
in synchronous mode the signal always starts at a phase angle
of 0° (synchronized with the system clock).
in
14