Safety Considerations Guide for Triconex General ... - ICEWeb

Alarm Usage 59
Alarm Usage
To implement the guidelines, the alarms described below are provided with TriStation 1131
software.
Programming Permitted Alarm
To remind the operator to lock out programming changes after a download change, or for
applications in which download changes are prohibited, connect the
ALARM_PROGRAMMING_PERMITTED output to an alarm.
Remote Access Alarm
In applications for which remote changes are not allowed, connect the
ALARM_REMOTE_ACCESS output to an alarm.
Response Time Alarm
Response time refers to the maximum time allocated for the controller to detect a change on an
input point and to change the state of an output point. Response time is primarily determined
by scan time (the rate at which the program is run), but is also affected by process time (how fast
the process can react to a change). The response time of the controller must be equal to or faster
than the process time. The scan time must be at least two times faster than the response time. To
meet the required response time of the process, set the MAX_SCAN_TIME input to less than 50
percent of the required response time. When the actual scan time as measured by the firmware
exceeds the MAX_SCAN_TIME value, the ALARM_RESPONSE_TIME output becomes true.
Disabled Points Alarm
A project should not contain disabled points unless there is a specific reason for disabling them,
such as initial testing. An alarm is available to alert the operator that a point is disabled.
Safety Considerations Guide for Triconex General Purpose v2 Systems