Omega Vehicle Security 1500 Configuring Alarms

Configuration Aspects for Programmers Appendix C

C-26 NetScan User’s Manual

Configuring Alarms

NetScan can produce an internal event when the value of a channel is outside of user-defined limits. These

“alarm events” can be used as trigger or stop events, or as a stimulus for TTL-level signals on the NetScan back

panel.

To use alarms the channels in question must be part of the channel scan. The alarms will become active and

monitored only after an acquisition has been configured and armed, and only at the programmed scan rate.

Note: To enable alarm monitoring prior to the trigger event, or to have an alarm condition serve as a

trigger event, you must first configure the acquisition with at least one pre-trigger scan.

Each channel has an associated high and low set point. Set points are defined as part of a channel configuration

using the C command. These set points create the “envelope” that constitutes the channel’s normal operating

range.

If the channel value goes above the high set point or below the low set point, the channel is in the alarm state. If

any channel configured by the C command is in the alarm state, a system alarm event is posted. For example, if

the trigger source is on Alarm, the alarm event would cause a trigger.

If desired, you can use an alarm event [for a specific channel] as a stimulus for a digital output signal (TTL) on

the back panel of the NetScan. This signal can be used to set off an audible alarm (user-supplied) or to inform

another device of the alarm condition.

Thirty-two digital alarm outputs are available o n the NetScan back panel. Although analog input c ha nnels on

the expansion chassis can be used to stimulate alarms, no digital output signals are available on the expansion

chassis. Regardless of the number of expansion chassis connected, no more than 32 digital alarm outputs are

available.

The Assign Alarm Output (A command) may be used to assign alarm conditions of various channels to one of

the 32 digital TLL level outputs located on the back panel. You can tie as many of the alarm conditions as you

want to any digital output. Use the C and A commands to configure alarm conditions for driving the digital

output lines (to enable alarm monitoring).

• The C command - determines the high and low setpoints and hysteresis of the alarm condition.

• The A command - assigns an input channel alarm to a digital output.

The following example indicates how to configure alarms and associate them with digital outputs for 24