Metrix GX1010 Notice De Fonctionnement page 103

unlike the FREQ= or EMF= parameter fields, the cursor does not move into the DC
OFFSET name because it has no alternative.
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; this is more fully explained in the Principles of Editing section.
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
with the cursor in the most significant digit, the rotary control will decrement the offset in
100mV steps as follows:
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, e.g. if the offset is +2.00V it can be changed
to-100mVbypressing +/-, 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 signal is being attenuated
the actual offset is shown in brackets as a non-editable field to the right of the set value.
For example, in the display below, the pk-pk output is not attenuated by the fixed attenuator
and the actual DC offset (in brackets) is the same as that set.
If the output level is now reduced to 250mV pk-pk, which introduces the attenuator, the
actual DC offset changes by the appropriate factor:
The above display shows that the set DC offset is +150mV but the actual offset is
+15.1mV. Note that the actual offset value also takes into account the true attenuation
provided by the fixed attenuator, using the values determined during the calibration
procedure. In the example displayed the output signal is 250mV pk-pk exactly and takes
account of the small error in the-20dB fixed attenuator; the offset is 15.1mV exactly, taking
account of the effect of the known attenuation (slightly less than the nominal -20dB) on the
set offset of 150mV.
Whenever the set DC offset is modified by a change in output level in this way a warning
message that this has happened will be displayed. Similarly, because the DC offset plus
16 - II
DC = +205.mV
DC = +205.mV
DC = +105.mV
DC = +5.00 mV
DC = -95.0 mV
DC = -195. mV
FREQ=10.00000kHz
EMF=+2.50 Vpp
DC=+150.mV (+150.mV)
SYM=50.0% (50.0%)
FREQ=10.00000kHz
EMF=+250.mVpp
DC=+150.mV (+15.1mV)
SYM=50.0% (50.0%)
50Ω Ω Ω Ω
50Ω Ω Ω Ω
GX1010