
Scans by ArtekMedia © 2007
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The External Trigger Mode
The external trigger mode provides external (remote) triggering of record
ings. To select the external trigger mode, use the trigger mode selector to
light the
EXTERNAL
indicator.
After selecting the external mode, a search for the external trigger is ini
tiated by pressing
DIRECT RECORD
(for a direct recording) or
FILL BUFFER
(for a
buffered recording). Recording can then be triggered by supplying a falling
edge (logic
1
to 0)
'TTL
level or contact closure to ground to the
EXT
TRIG
(external trigger) connector
on
the right side panel.
Post- or pre-trigger time settings may be used for externally triggered, buf
fered recordings. However, only post-trigger time settings may be specified
for externally triggered, direct recordings (prc-trigger selections are
ignored).
The
EXT TRIG
connector accepts a male BNC connector,
and is
normally
pulled high (logic
1
at 5-volt
TTL
level). After
initiating
a trigger search in
the external trigger mode, a TfL-Ievel transition from high to low (logic 1
to 0) applied to the
EXTTRIG
connector will trigger the recording. The record
ing may also be triggered by contact closure of the positive terminal of the
connector to the connector's ground terminal.
The Internal Trigger Mode
With the internal trigger mode, you can specify signal voltage and slope
requirements that must be met by the Channel ! input to trigger a record
ing. After specifying the requirements and initiating a trigger search, the
HP 7090 continuously monitors the Channel !
input
until the signal meets
the requirements, at which time triggering occurs. Although triggering is
via the Channel l input only, any of the channel inputs may he selected for
recording
in
the direct recording mode, and all of the channel buffers are
filled normally for the buffered recording mode.
Post- or pre-trigger time settings generally may be used for internally trig
gered, buffered recordings. Only post-trigger time settings, however, may
he used for internally triggered direct recordings (pre-trigger
times
are
ignored).
Four internal trigger options are available - above level, below level, out
side
window,
and inside
window. Select the desired option by using the
trigger mode
selector
to light the appropriate indicator. The
TRIGGER LEVEL
and
TRIGGER WIDTH
setup
conditions are then used to define the Channel !
signal requirements, as described in.the following sections.
The External
Trigger Connector
Trigger Modes and Operations
5-3