Omron DRT2 SERIES DEVICENET SLAVES - OPERATION MANUAL 04-2008 Operation Manual page 439

Temperature Input Terminals
Setting Hysteresis
418
When each of these values is exceeded, the Comparator Result Flag in the
area for Analog Status Flags is turned ON. If an alarm has not occurred, the
Normal Flag (pass signal) will be ON.
Set values
Comparator Result Flag
(in Analog Status Flags)
ON/OFF
Note When the temperature input value changes faster than the conversion cycle,
the status may go from a Low Limit alarm directly to a High Limit alarm without
having the Normal Flag (pass signal) go ON in between. Configure ladder
programs to prevent this from occurring.
The Comparator Result Flag turns OFF when the value is lower than the hys-
teresis width (H or HH alarm occurs) or exceeds it (L or LL alarm occurs), as
shown in the following diagram. If the analog value fluctuates around the
threshold, and the flag repeatedly turns ON or OFF, setting hysteresis will sta-
bilize the flag operation. The setting range is 0 to 16,383.
HH set value or
H set value
HH Alarm Flag or
H Alarm Flag
Note When setting the hysteresis value, adjust for each input's decimal point posi-
tion or the 1/100 display mode if the 1/100 display mode is being used. Always
correct the hysteresis value after changing the display mode setting or replac-
ing the sensor with a sensor that has a different decimal point position.
Example hysteresis value settings for 10 ° C:
• R thermocouple (normal display) setting: 0010 decimal
• T thermocouple (normal display) setting: 0100 decimal
• Setting for any input with 1/100 display: 1000 decimal
HH
H
L
LL
HH alarm
H alarm
Normal Flag
(Pass signal)
L alarm
LL alarm
Hysteresis width
LL set value or L
set value
LL Alarm Flag or
L Alarm Flag
Section 7-6
Hysteresis
width