Omron GRT1 - 11-2007 Operation Manual page 222

Temperature Input Units
Setting Hysteresis
Note
OFF Delay
When any of these values is exceeded, the Comparator Result Flag in the
area for Temperature Status Flags turns ON. If an alarm does not occur, the
Normal Flag (pass signal) turns ON.
Set values
Comparator Result Flag
(in Temperature Status
Flags) ON/OFF
Note If the temperature input value changes faster than the conversion cycle, the
High Limit alarm may turn ON without the Normal Flag (pass signal) turning
ON for the Low Limit alarm. Configure ladder programs to prevent this occur-
ring.
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 temperature 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 from 0 to 16383.
HH set value or
H set value
HH Alarm Flag or
H Alarm Flag
When setting the hysteresis value, adjust for each input's decimal point posi-
tion and the 1/100 Display Mode (if it is being used). Always correct the hys-
teresis value after changing the display mode setting or changing to an input
that has a different decimal point position.
The time until the Comparator Result Flag turns OFF can be extended. For
example, even if the Flag is ON momentarily, the OFF delay can be set so that
the Master can receive notification of the Flag's status.
HH set value
HH Alarm Flag
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
Hysteresis width
OFF delay
Section 6-4
Hysteresis
width
201