Metrix GX1010 Notice De Fonctionnement page 102

Vrms the DC Offset (see next section) is ignored in the calculation and must be taken into
consideration by the user if the DC Offset is non-zero.
The desired form of the output level display can be selected whilst the edit cursor is in the
parameter name field by stepping through all the options with the DIGIT keys or the rotary
control; bring the cursor to the parameter name field first, if necessary, by pressing
EMF/PD, or by using the FIELD keys.
With the appropriate parameter form selected, the value is entered as a number followed
by units, e.g. 100mV can be entered as 1, 0, 0, mV or ·, 1, V etc. The software acts
intelligently in certain situations; for example, even if EMF or PD is the selected parameter
form, entering a number followed by the dBm key will cause the number to be entered as
dBm. Similarly, with dBm as the selected parameter form, entering a number followed by V
or mV will cause the number to be entered as PD=Vrms. 0dBm is 1mW into the specified
impedance; low signal levels are specified by using the +/- key to enter negative dBm. See
also the last paragraph of this section for the use of the +/- key for output inversion.
Moving the edit cursor to the numeric field permits the set value to be varied by the rotary
control in steps determined by the cursor position within the field. The FIELD keys move
the cursor to the field and the DIGIT keys move it within the field; this is explained more
fully in the Principles of Editing section.
Moving the edit cursor to the units field permits the numeric value to be changed in decade
steps by the DIGIT keys or rotary control; the decimal point will move and/or the units will
change as appropriate. Further increments are inhibited if the next decade step would take
the value above the maximum level or below the minimum level. Decade stepping with the
DIGIT keys or rotary control is also inhibited when the level is displayed in dBm.
Wherever the cursor is positioned on the second line of the display, alternate presses of
the +/- key will invert the MAIN OUT output; if DC OFFSET is non-zero, the signal is
inverted about the offset. The one exception to this is if the output level is specified in dBm;
since low signals are specified in -dBm, the - sign is interpreted as part of a new output
level entry and not as a command to invert the signal. The output level must be shown as
an EMF or PD value for the +/- key to operate as a signal invert key.
If an amplitude change is made which involves switching the attenuator, the output is
switched off for 45ms whilst the change is made to prevent any transients appearing at the
output.
4.2.1.3. 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
50Ω and 600Ω. The output level is unchanged but the displayed value in dBm will change
because the 0dBm reference level (1mW into the specified impedance) changes with the
impedance.
4.2.1.4. 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. 100mV 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 position the cursor, before making the number and unit entry. Note that,
GX1010
FREQ=10.00000kHz
EMF=+20.0 Vpp
DC=+0.00mV (+0.00mV)
SYM=50.0% (50.0%)
50Ω Ω Ω Ω
II - 15