Reference Manual
00809-0100-4841, Rev. AA
May 2007
4-55
Rosemount 3490 Series
P254 Interval (Factory default is "1:00" i.e. 1hr 0min)
This is for defining the interval for repeating a Custom relay operation. P255
and P256 are for setting up a second starting time and an associated interval.
P257 Max Retries (Factory default is 10)
This defines the maximum number of failed attempts to perform Custom relay
operations before it is deemed an alarm condition. This situation can occur if
the 3490 Series Control Unit is off-line, preventing all Custom relay operations
from starting. In addition, it can occur when the maximum On time (relay
safeguard, page 4-43) for a relay prevents a Custom relay operation from
completing. For alarm indication options, see Section “About Alarms“ on
page 4-60.
Table 4-14.
P250/P251/P252 Options
Relay Operations Alarm
(Special alarm - see Table 4-12 on page 4-45)
P491 RL operations (Factory default is 0)
It is an alarm condition when the number of operations of a specified relay
(P492) exceeds the number in P491. For alarm indication options, see “About
Alarms“ on page 4-60.
P492 RL ops rly sel (Factory default is "Disabled")
Select the relay for the monitoring operation associated with parameter P491.
Relay operation counters are parameters D811 to D815, located in the
MONITOR menu - see “Health Check: 3490 Series Control Unit“ on page 5-2.
Relay Run Time Alarm
(Special alarm - see Table 4-12 on page 4-45)
P493 RL runtime (Factory default is 0:00 h:m = OFF)
It is an alarm condition when a specified relay (P494) has been energised for
longer than the period (hours and minutes) defined by P493. For alarm
indication options, see “About Alarms“ on page 4-60.
P494 RL run rly sel (Factory default is "Disabled")
Select the relay for the monitoring operation associated with parameter P493.
Options
(1)
(1) Abbreviations: "Ext Trig" = External Trigger (Digital Input)
Purpose of option P250 P251 P252
None Switched off Yes Yes Yes
Time P253 and P254 determine when the relay
is to be energised
Yes Yes -
PV > Level While PV value (D800) is greater than On
point for relay, energise relay
Yes - -
PV < Level De-energise relay when PV value (D800)
less than the On point for relay
- Yes Yes
Ext Trig Energise a relay only while a digital input
is active. This does not require Digital
Input IN1 or IN2 to be allocated an action
-YesYes
Ext Trig Xs If Digital Input is active, energise relay
after X seconds delay. This does not
require Digital Input IN1 or IN2 to be
allocated an action
- - Ye s
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