Rohde & Schwarz Hameg HM8150, User Manual

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Operation of the HM8150
Only pulse durations within the permissible range for the
selected frequency are displayed. Attempts to set a time
value outside of this range will cause a beep and the entry
will not be accepted. The maximum pulse width is defined
by the following formula:
Pulse width = 0.8 / Frequency
The displayed value refers to the positive pulse duration, if
the INVERT function is not enabled. In the inverted mode
(INVERT button
9
is illuminated) negative pulses are gene-
rated. In this case, the time for the negative pulse width is
shown in the display. If the sweep function is enabled, the
pulse width is determined by the start or stop frequency
whichever is higher.
4.7 Amplitude
Before setting the amplitude the AMPL button
12
has to
be operated to enable the amplitude setting mode. The
AMPL button is illuminated, if the signal amplitude can be
changed. In the right part of the display the current ampli-
tude is shown. The amplitude is changed like described in
chapter “Frequency“.
The value shown in the display
4
is the peak-to-peak
voltage for the output without load. Pulses start at the zero
crossing and are either positive or negative, depending on
whether the INVERT function is activated (the INVERT LED
is lit). The positive or negative signal amplitude – in refe-
rence to the baseline – is then shown in the display.
The ranges for setting the output amplitude are:
Without load into 50 Ω
Range 1 2.1 V to 20 V 1.05 V to 10 V
Range 2 0.21 V to 2.0 V 0.105 V to 1 V
Range 3 20 mV to 200 mV 10 mV to 100 mV
The next highest or next lowest range is being automati-
cally switched to when the limits of the current range are
exceeded. When the output is terminated with 50 Ω the
values shown in the display must be divided by 2 to get
the correct value. If an offset voltage is added, then it may
not be in a higher range than the amplitude setting.
4.8 Offset
The output signal can be superimposed with a negative
or positive DC offset. This function is enabled by pressing
the OFFSET button
11
. A luminous button indicates that
the offset is active.
Before setting the offset the OFFSET button 7 has to be
operated to enable the offset setting mode. The OFFSET
button is illuminated, if the offset can be changed. In the
right part of the display the current offset is shown. The
offset is changed like described in chapter “Frequency“.
The maximum possible offset voltages are as follows:
Range1
± 7.5 V
Range2 ± 0.75 V
Range3 ± 75 mV
The offset voltage must be in the same range as the
value selected for the amplitude of the output signal. An
offset of 5 V cannot be used for a signal voltage of 20 mV.
Within a given range, the offset voltage can be varied con-
tinuously from negative to positive values. The same con-
ditions apply for the use of the offset with the sweep
function.
4.9 Signal output
The signal output of the HM8150 has an impedance of
50 Ω and can be switched on and off using the OUT-
PUT button
8 . A luminous button indicates that the out-
put is active. If an offset voltage is being used, it is swit-
ched on and off by the OFFSET button
7
. The INVERT
button
9
is used to reverse the polarity of the output sig-
nal. The output is short circuit-proof and protected against
reverse voltages (AC and DC) for a short time (approx. 15
seconds).
4.10 Sweep mode
In the frequency sweep mode, the function generator
HM8150 “steps” from the start frequency to the stop fre-
quency during a sweep time which you specify. If the start
frequency was chosen lower than the stop frequency the
sweep will run from the lower to the higher frequency. If
the start frequency was chosen higher than the stop fre-
quency the sweep will run from the higher to the lower
frequency.
The HM8150 can produce a frequency sweep for sine
wave, square wave, sawtooth, pulse and arbitrary
waveforms.
Sweep mode can be additionally enabled to supplement
the operating modes continuous and triggered. It is activa-
ted by pressing the ON button
16
and is indicated by
illumination of the button. The parameters sweep time
(TIME), start frequency (START) and stop frequency (STOP)
can be set independently of each other.
Fig. 4.3: Swept sine wave; sawtooth output
The sweep function can not be enabled during gated mode.