Section 5
Page 5 - 12
HA243821
Issue 5 Mar 98
MODEL 346 INSTALLATION AND OPERATION MANUAL
5.4 TRACE HISTORY
5.4.1 INTRODUCTION
This feature stores pre-event trace history for a channel and replays it when commanded to by an event (internal
trigger, see section 3.4) or manual selection from the operator menu (see section 3.3). Because each playback
gives the most recent pre-event history, repeated playback of the same history is not possible.
The channel input is sampled and stored at a rate determined by the history chart speed selected. Actual playback
is done at the fastest practical chart speed. The playback chart span can be different from the span of the stored
channel. A single ‘magnification’ factor can be applied to all selected channels as they are played back.
The time period of trace history that can be stored is related to the selected history chart speed. 75 mm of chart
record is stored (1.5 hrs. of record at a history chart speed of 50 mm/hr). Faster chart speeds require more stored
data values and decrease the time period of the trace history that can be stored.
In order to present the complete picture of conditions surrounding an event, an additional 75 mm of post-event
data is stored starting at the event which triggered history.
The post-event data is then played back on the chart at maximum speed after the trace history. Replay ends when
it catches up with ‘real-time’ or when the content of the chart buffer has been printed. Current data is followed by
the printing of all history scales in Break-trace Mode (chart timing is interrupted).
5.4.2 CONFIGURATION PAGES
CHART SPEED
This selection determines the time period of the replayed record on the chart. The Up/-Down/Side Arrow keys are
used to enter the History Chart Speed. To determine the time (in hours) covered by Trace History, the selected
History Chart Speed is divided into 75 mm (3 in). (See examples in the table below.)
MAGNIFICATION FACTOR
The playback of History can use the Configured Channel Range or it can be ‘Magnified’ to a different Range.
Although it operates similarly, this is not the same Range Magnify function as that described in the next section
(5.5). The Up/Down/Side Arrow keys are used to set the single Magnification Factor (between .05 and 20) for all
History Traces selected for Magnification.
MAGNIFICATION CENTRE
A value can be set up in the channel configuration to act as a centre point for the magnification function. If such
a value is not entered, the range history will be centered about the input value at the time ‘history’ is requested.
History
chart speed
(mm/hr)
20
100
300
3000
History
time
3.75 hours
45 minutes
15 minutes
1.5 minutes