Echelon i.LON SmartServer 2.0 - Manual (Page 89)

i.LON SmartServer 2.0 Programmer’s Reference 6-11
Offset Limit Alarm Generated When.... Alarm Status
Input Value>Compare Value +
UCPThighLimit1Offset AL_HIGH_LMT_ALM1
Input Value>Compare Value +
UCPThighLimit2Offset AL_HIGH_LMT_ALM2
Input ValueUCPTlowLimit1Offset AL_LOW_LMT_ALM1
Input ValueUCPTlowLimit2Offset AL_LOW_LMT_ALM2
Each time an alarm is generated based on any of these offset limits, the value of the input data point
must return to a value inside the hysteresis range for that limit, and the time period specified by the
property must elapse, before the alarm is cleared. Only then could another alarm be
generated based on that offset limit.
The Alarm Generator’s hysteresis levels determine the value the input data point must return to for
each alarm condition to be cleared. The following table describes how these levels are calculated for
each of the offset limits listed above.
Offset Limit Causing Alarm Alarm Cleared When...
Input Value<=Comp Value+ UCPThighLimit1Offset –
SCPThysHigh1
Input Value<=Comp Value+ UCPThighLimit2Offset –
SCPThysHigh2
Input Value>= Compare Value – UCPTlowLimit1Offset +
SCPThysLow1
Input Value>= Compare Value – UCPTlowLimit2Offset +
SCPThysLow2
When an alarm is cleared, the data point is updated to the next lowest alarm level. For example, when
an AL_LOW_LMT_ALM_2 alarm is cleared, the data point is updated to AL_LOW_LMT_ALM_1.
When that condition clears, the data point is updated to AL_NO_CONDITION. The following table
describes this process in more detail.
Event Input Data Point Status Comments
Value of input data point is
normal. AL_NO_CONDITION No alarm condition.
Value of input data point
goes above first level
(UCPThighLimit1Offset). AL_HIGH_LMT_ALM1 Updated to the first alarm
condition.
Value of input data point
goes above second level
(UCPThighLimit2Offset). AL_HIGH_LMT_ALM2 Updated to the second, and more
severe, alarm condition.