Agilent Technologies 34901A User Manual page 131

Chapter 4 Features and Functions
Alarm Limits
Using the Alarm Output Lines
Four TTL alarm outputs are available on the rear-panel Alarms
connector. You can use these hardware outputs to trigger external
alarm lights, sirens, or send a TTL pulse to your control system. You can
assign an alarm to any configured channel and multiple channels can be
assigned to the same alarm number. Each alarm output line represents
the logical " OR " of all channels assigned to that alarm number (an alarm
on any of the associated channels will pulse the line).
Alarms Connector
You can configure the behavior of the alarm output lines as described
below. The behavior of the alarm annunciators on the front panel also
tracks the alarm output configuration. The configuration that you select
is used for all four alarm output lines. A Factory Reset (*RST command)
clears all four alarm outputs but does not clear the alarm queue in
either configuration.
• Latch Mode: In this mode, the corresponding output line is latched
true when the first alarm occurs and remains asserted until you clear
it by initiating a new scan or cycling power. You can manually clear the
output lines at any time (even during a scan) and the alarm data in
memory is not cleared (however, data is cleared when you initiate
a new scan).
• Track Mode: In this mode, the corresponding output line is asserted
only when a reading crosses a limit and remains outside the limit.
When a reading returns to within limits, the output line is
automatically cleared. You can manually clear the output lines at any
time (even during a scan) and the alarm data in memory is not
cleared (however, data is cleared when you initiate a new scan). The
alarm outputs are also cleared when you initiate a new scan.
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Alarm 4 Output
Alarm 3 Output
Alarm 2 Output
Alarm 1 Output
or
Gnd