Product Manual

Sum
Internal Sum12
mid-range then the SUM signal needed to force the output to range maximum is halved
to approximately 1 V p-p.
To facilitate the setting of appropriate sum and amplitude levels the output amplitude of
the selected channel can also be changed from the
SUM set-up screen. Press the CHx
soft-key and adjust the amplitude with direct keyboard entries or by using the rotary
control.
External sum cannot be used with internal modulation.
Internal Sum
Pressing the SUM key calls the SUM set-up screen:
SUM source: CH1
ratio: 1.00000
CH2 +2.00 Vpp
CH1 +1.00 Vpp
Pressing the source soft-key steps the sum source between off, external and
CHx (
where x is the number of the previous channel). CHx is the source of the
internal sum signal.
With
CHx selected for internal sum the screen is as shown above. The amplitude of
both the summing channel,
CHx+1, and the internal sum signal, CHx, are shown in
the display, together with the
ratio in which they are added. All three parameters can
be selected with the appropriate soft-key and set directly from the keyboard or by the
rotary control. Changing any one parameter will also adjust one of the other two; for
example adjusting the amplitude of either channel will cause the displayed ratio to
change.
The value shown in the
ratio field is the CHx amplitude divided by the CHx+1
amplitude. Adjusting the ratio value directly changes the amplitude of the sum input
signal, CHx, not the channel’s output amplitude. When a value is entered into the
ratio
field it is initially accepted as entered but may then change slightly to reflect the
actual ratio achieved with the nearest sum input amplitude that could be set for the given
channel output amplitude.
Warnings are given when either a ratio, sum input or output amplitude change is
attempted which would cause the channel's output to be driven into clipping.
In general it is recommended that the amplitude of the sum input is not greater than the
channel amplitude, i.e. the ratio is less than or equal to 1; most ratio values can be set,
down to very small signal levels. If the sum input is greater than the channel amplitude
there will be combinations when the ratio can be set to a little greater than 1. Note that
the software will always accept an entry, make the calculation and, if the combination is
not possible, return the instrument to its last legitimate setting.
The amplitude of the channel being used for the internal sum signal can still be adjusted
on its own
AMPLITUDE set-up screen; its status screen shows the message x to
indicate that it is being used as a source for channel x.
Internal sum cannot be used with internal modulation.
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