Fluke DDS Function Generator 271, User Manual

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271
Users Manual
5-4
output level entry and not as a command to invert the signal. Thus the output level must
be shown as a
VhiZ
or
V
value for the
+/-
key to operate as a signal invert key.
If an amplitude change is made which involves switching the stepped attenuator, the
output is switched off for 45 ms whilst the change is made to prevent any transients
appearing at the output.
Output Impedance
The impedance of the
MAIN OUT
output is selected in the last field of the second line.
Move the edit cursor to this field and use the DIGIT keys or rotary control to toggle
between
50
Ω
and
600
Ω
. The output level is unchanged but the displayed value in
dBm will change because the 0 dBm reference level (1 mW into the specified impedance)
changes with the impedance.
DC Offset
The dc offset is set on the third line of the main menu. With the cursor anywhere in the
third line the dc offset can be changed directly from the keyboard by entering the number
and appropriate units, e.g. 100 mV can be set by entering
1
,
0
,
0
,
mV
or
.
,
1
,
V
, etc. If the
cursor is not already in the third line of the display it is first necessary to press the
DC OFFSET
key to reposition the cursor, before making the number and unit entry.
Note that, unlike the
FREQ=
or
VhiZ=
parameter fields, the cursor does not move
into the
DC OFFSET
name because the dc offset has no alternative representation.
With the edit cursor in the numeric field, turning the rotary control will increment or
decrement the numeric value in steps determined by the edit cursor position within the
field. The
DC OFFSET
or
FIELD
keys move the cursor to the field and the
DIGIT
keys
move it within the field.
Because dc offset can have negative values, the rotary control can take the value below
zero; although the display may autorange to a higher resolution if a step takes the value
close to zero, the increment size is maintained correctly as the offset is stepped negative.
For example, if the display shows
DC = +205. mV
with the cursor in the most significant digit, the rotary control will decrement the offset in
100mV steps as follows:
DC = +205.mV
DC = +105.mV
DC = +5.00 mV
DC = -95.0 mV
DC = -195. mV
The
+/-
key can also be used at any time to set the offset value negative; alternative
presses toggle the sign between
+
and
-
. Alternatively the sign of the offset can be
changed as part of the entry of a new value. For example, if the offset is +2.00 V it can be
changed to -100 mV by pressing
+/-
,
1
,
0
,
0
,
mV
.
The actual dc offset at the
MAIN OUT
socket is attenuated by the fixed-step output
attenuator when this is in use. Since it is not obvious when the attenuator steps are
changed the actual offset is shown in brackets as a non-editable field to the right of the
set value.
1.888.475.5235 info@Fluke-Direct.com
Fluke-Direct
.com