User's Manual

Parameter reference
SITRANS LR250 (FOUNDATION FIELDBUS)
158 Operating Instructions, 01/2014, A5E32221411-AB
Low Limit Warning (2.6.6.3.)
The setting for the lower warning limit in AIFB1 units.
Values
Range: -Infinity to Infinity
Default: -Inf
Low Limit Alarm (2.6.6.4.)
The setting for the lower alarm limit in AIFB1 units.
Values
Range: -Infinity to Infinity
Default: -Inf
Limit Hysteresis (2.6.6.5.)
Hysteresis is used to adjust the sensitivity of the trigger for alarm messages. It is used to
compensate when a process variable fluctuates around the same value as a limit. A high level
alarm occurs when a value exceeds an upper limit. The alarm’s status remains true until the
value drops below the limit minus the alarm hysteresis. The directions are reversed for low limit
detection.
Values
Range: 0 to 50
Default: 0.50
Enter a value for the hysteresis here, to be used for all warnings and alarms. The units are the
same as the Output scale, i.e. AIFB1 units.
Display (2.6.7.)
Filter Time Constant (2.6.7.1.)
The time constant for the damping filter. The damping filter smooths out the response to a
sudden change in level. This is an exponential filter and the engineering unit is always in
seconds. See Damping (Page 238) for more detail.
Values
Range: 0 to 600 s
Default: 0
a)
a) To meet accuracy specification, Filter Time Constant (PV_FTIME) must be changed from
default of 0.0 s to a minimum of 10.0 seconds [see Performance (Page 198)].