Rosemount 3491, Справочное руководство, Страница: 88 / 152

Reference Manual
00809-0100-4841, Rev. AA
May 2007
Rosemount 3490 Series
4-56
Run time counters for all relays are D821 to D825, located in the MONITOR
menu - see “Health Check: 3490 Series Control Unit“ on page 5-2.
No Activity Alarm
(Special alarm - see Table 4-12 on page 4-45)
P497 No Activity Del (Factory default is 0:00 h:m)
It is an alarm condition if there is no relay activity for the period (hours and
minutes) defined by parameter P497. This is to be used with parameter P498.
The alarm condition is cleared when any monitored relay is energised. For
alarm indication options, see “About Alarms“ on page 4-60.
P498 No Activity RL (Factory default is 00000)
Select relays for monitoring operation associated with relay inactivity. Each
digit represents a relay. Relay RL1 is selected for monitoring by editing the
first digit to be a "1". Similarly, relay RL5 is selected with the fifth digit. To
de-select a relay, change the appropriate digit back to a "0". This parameter is
to be used with parameter P497.
Rising Level Alarm
(Special alarm - see Table 4-12 on page 4-45)
P490 R Lev alrm del (Factory default is 0:00 m:s)
The rising level alarm requires at least one Assist or Standby relay.
If any Standby relay is energised, monitoring of the rising level is enabled.
However, in the case of Assist relays, they must all be energised for
monitoring of the rising level to be enabled.
Once the monitoring is enabled, a timed delay (P490) starts. After the delay
time (P490) and the level is still rising, there will be a 'Rising Level' alarm
condition if the Rate of Change of the PV is positive. The alarm stops when
the Rate of Change of the PV is negative, indicating a falling level.
For the Rising Level Alarm to be indicated by a relay or the Current Output, a
method must be selected - see “About Alarms“ on page 4-60.
Also, see Section “Rate of Change Relay“ on page 4-53 for details of the Rate
of Change calculation.
Pump Efficiency Alarm (Models 3491 and 3492 only)
(Special alarm - see Table 4-12 on page 4-45)
The pump efficiency feature allows you to indicate an alarm (P550, P4x1) if
the calculated pump efficiency falls below a defined limit (P495).
P495 Pump effy limit (Factory default is 0% = OFF)
It is an alarm condition if the calculated pump efficiency falls below the limit
defined by P495 in %. The pump efficiency calculation is based on the Rate of
Change of the 3490’s PV and is independently monitored for each selected
relay (P496),
For alarm indication options, see “About Alarms“ on page 4-60.
P496 Pump effy RL (Factory default is 0000)