Fluke DDS Function Generator 271, User Manual

Page: 40 / 132

271
Users Manual
5-6
For example, in the display below the frequency is set to 100 kHz and a square ware is
selected.
FREQ=100.0000kHz
VhiZ=+20.0 Vpp 50
Ω
DC=+0.00mV (+0.00mV)
SYM=90.0% (80.0%)
The symmetry is set to 90 % but the actual symmetry is 80 %, which is the limit for
square waves and pulse waveforms above 30 kHz.
The flashing cursor can be moved within the field using the
DIGIT
keys; turning the
rotary control will then increment or decrement the setting in steps determined by the
position of the cursor in the field.
Should the symmetry be set outside the permitted range for the selected frequency and
waveform combination a warning message will be shown on the display (see
Warnings
and Error Messages
below).
Warning and Error Messages
Two classes of message are displayed on the screen when an illegal combination of
parameters is attempted.
WARNING
messages are shown when the entered setting causes some change which the
user might not necessarily expect. Examples are:
1. Changing the amplitude (VhiZ) from 2.5 Volts p-p to 250 mV p-p brings in the step
attenuator; if a non-zero offset has been set then this will now be attenuated too. The
message
DC OFFSET CHANGE BY OUTPUT LEVEL
will be shown temporarily
on the screen but the setting will be accepted; in this case the actual, attenuated, offset
will be shown in brackets to the right of the set value.
2. With the output level set to 10 V p-p, increasing the dc offset beyond ±5 V will cause
the message
DC LEVEL MAY CAUSE CLIPPING
. The offset
change will be accepted (producing a clipped waveform) and the user may then
choose to change the output level or the offset to produce a signal which is not
clipped.
3. With 100 kHz square wave selected, increasing symmetry beyond 80 % will cause the
message
SYMMETRY TOO WIDE FOR FUNC/FREQ
to be displayed. The setting
will be accepted but the actual symmetry will be limited to 80 % as shown in the
bracketed field beside the setting. If this out-of-specification setting is changed by
reducing the frequency below 30 kHz or by changing the waveform then the warning
SYMMETRY CHANGED BY FUNC/FREQ
is displayed.
ERROR
messages are shown when an illegal setting is attempted, most generally a
number outside the range of values permitted. In this case the entry is rejected and the
parameter setting is left unchanged. Examples are:
1. Entering a frequency of 100 MHz.
The error message
FREQUENCY/PERIOD VAL OUT OF RANGE
is shown.
2. Entering a VhiZ of 25 V p-p.
The error message
MAX OUTPUT LEVEL EXCEEDED
is shown.
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