Agilent Technologies L4400 - Manual (Page 100)

88 L4400 User’s Guide
3 Operating and Programming
Using the Alarm Output Lines
As mentioned, there are two TTL alarm lines available on the rear- panel
Alarms connector. 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). The connector is shown below:
5
1
9 6
Alarm 1 output (pin 1)
Alarm 2 output (pin 2)
Gnd (pin 9)
or

Figure 3-15. The L4400 Series Rear Panel Alarm Connector.
You can configure the behavior of the alarm output lines as follows. The
configuration that you select is used for both alarm output lines. A
Factory Reset (
*RST command) clears the 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.
• You can control the slope of the pulse from the alarm outputs (the
selected configuration is used for both outputs). In the falling edge
mode, 0V (TTL low) indicates an alarm. In the rising edge mode, +5V
(TTL high) indicates an alarm. A Factory Reset (
*RST command) will
reset the slope to falling edge.


Note: Changing the slope of the output lines may cause the lines to
change state.