Endress+Hauser PROline Prosonic Flow 93 Function Manual page 198

6 PID function block (PID controller)
198
PID function block (PID controller) / base index 810
Parameter Write access
with operating
mode
(MODE_BLK)
ALARM_HYS ROUT - RCAS -
CAS - AUTO -
MAN - OOS
PROline Prosonic Flow 93 FOUNDATION Fieldbus
Description
Entry of the hysteresis value for the upper and lower warning or
alarm limit values. The alarm conditions remain active as long as
the measured value is within the hysteresis. The hysteresis value
affects the following warning and alarm limit values of the PID
function block:
• HI_HI_ALM (upper limit value alarm)
• HI_ALM (upper limit value warning)
• LO_LO_ALM (lower limit value alarm)
• LO_ALM (lower limit value warning)
• DV_HI_ALM (limit value for upper control deviation)
• DV_LO_ALM (limit value for lower control deviation)
User input:
0...50%
Factory setting:
0.5%


Note!
The hysteresis value relates to a percentage of the range of the
PV_SCALE parameter in the PID function block, (see Page 213).
Example:
The top diagram shows the defined LO_LIM and HI_LIM alarm
limit values with their respective hystereses (grey background)
and the signal curve of the process variable PV.
The bottom two diagrams show the behaviour of the associated
HI_ALM and LO_ALM alarms in relation to the changing signal
curve (0 = no alarm, 1 = alarm output).
a = Process variable PV exceeds the limit value HI_LIM, HI_ALM
is activated.
b = Process variable PV undershoots the hysteresis value of
HI_LIM, HI_ALM is deactivated.
c = Process variable PV undershoots the limit value LO_LIM,
LO_ALM is activated.
d = Process variable PV exceeds the hysteresis value of LO_LIM,
LO_ALM is deactivated.
Endress+Hauser