Agilent Technologies L4400 manual Using the Alarm Output Lines

3Operating 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:

1

6

Alarm 1 output (pin 1) Alarm 2 output (pin 2)

5

9

or

Gnd (pin 9)

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.

88 L4400 User’s Guide