Echelon MPR-50 Multi-Port Router User Manual
Page 38
• Ch
In the L
ON
M
ARK
guidelines, the possibility exists for two limit levels (levels 1 and 2)
for each of the low and high limits. The MPR-50 implements a single limit according
to the following rules:
1. If the alarm type was not AL_HIGH_LMT_ALM_1 and the value is now greater
than SCPThighLimit1, then the alarm type becomes AL_HIGH_LMT_ALM_1.
2. If the alarm type was AL_HIGH_LMT_ALM_1 and the value drops below
SCPThighLimit1
minus SCPThystHigh1, then the alarm type becomes
AL_HIGH_LMT_CLR_1
. For high limit alarms, the hysteresis value is used only to
subtract from the limit value.
3. If the alarm type was not AL_LOW_LMT_ALM_1 and the value is now less than
SCPTlowLimit1
, then the alarm type becomes AL_LOW_LMT_ALM_1.
4. If the alarm type was AL_LOW_LMT_ALM_1 and the value rises above
SCPTlowLimit1
plus SCPThystLow1, then the alarm type becomes
AL_LOW_LMT_CLR_1
. For low limit alarms, the hysteresis value is used only to
add to the limit value.
The nvoIvalCrcErr and nvoIvalMissed variables have a high alarm limit
(SCPThighLimit1) and do not have a low alarm limit. A hysteresis value
(SCPThystHigh1) is used to prevent oscillation of the alarm condition when it is
near the high alarm limit value. The high alarm is enabled by default via the
SCPThighLimit1Enable
property.
The nvoIvalBandUtl variable has both a high alarm limit (SCPThighLimit1) and
a low alarm limit (SCPTlowLimit1). The high alarm is enabled by default via the
SCPThighLimit1Enable
property, and the low alarm limit is disabled by default
via the SCPTlowLimit1Enable property. The low alarm limit can be useful to
detect that, for instance, a certain level of background heartbeat traffic expected on a
channel has slowed or stopped—which indicates a power, channel wiring, or other
problem. If the low alarm limit is enabled, also set the SCPTlowLimit1 property to
a non-zero value that is slightly below the expected level of background heartbeat
traffic. Hysteresis values (SCPThystHigh1 and SCPThystLow1 as appropriate) are
used to prevent oscillation of the alarm condition when it is near the alarm limit
value.
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MPR-50 Monitor