Yokogawa Electric Corporation - TC10 - ENGINEERING MANUAL - PAG. 13
reset can be done only by an external command
(
button, digital inputs or serial link).
Alarm reset
Alarm reset
AL1
PV
time
off
off
Ab1 = +2
Ab1 = +0
off
off
ON
ON
3.
An “Acknowledgeable” alarm is an alarm that can
be reset even if the conditions that generated the
alarm are still present. Alarm acknowledge can
be done only by an external command (
button,
digital inputs or serial link).
Alarm ACK
Alarm ACK
AL1
PV
time
off
off
Ab1 = +4
Ab1 = +0
off
off
off
ON
ON
ON
A “relative alarm not active at set point change”
is an alarm that masks the alarm condition after
a set point change until process variable reaches
the alarm threshold ±hysteresis.
Sp2
Sp1
PV
time
Ab1 = +8
Ab1 = +0
ON
off
off
AL1
off
off
off
AL1
ON
ON
ON
ON
4.
The instrument does not store in EEPROM the
alarm status. For this reason, the alarm status
will be lost if a power down occurs.
[30] AL1L - For High and low alarms it is the low
limit of the AL1 threshold
- For band alarm it is low alarm threshold
Available:
When [28] AL1t is different from “nonE” or [28]
AL1t is different from “SE.br”.
Range:
From -1999 to [31] AL1H engineering units.
[31] AL1H - For High and low alarms, it is the high
limit of the AL1 threshold
- For band alarm, it is the high alarm
threshold
Available:
When [28] AL1t is different from “nonE” or [28]
AL1t is different from “SE.br”.
Range:
From [30] AL1L to 9999 engineering units.
[32] AL1- Alarm 1 threshold
Available:
When:
[28] AL1t = LoAb - Absolute low alarm;
[28] AL1t = HiAb - Absolute high alarm;
[28] AL1t = LodE - Deviation low alarm (relative);
[28] AL1t = LidE - Deviation high alarm (relative).
Range:
From [30] AL1L to [31] AL1H engineering units.
[33] HAL1 - Alarm 1 hysteresis
Available:
When [28] AL1t is different from “nonE” or
[28] AL1t is different from “SE.br”.
Range:
1 to 9999 engineering units.
Notes: 1.
The hysteresis value is the difference between
the Alarm threshold value and the point the Alarm
automatically resets.
2.
When the alarm threshold plus or minus the
hysteresis is out of input range, the instrument
will not be able to reset the alarm.
Example:
Input range 0 to 1000 (mBar).
–
Set point equal to 900 (mBar);
–
Deviation low alarm equal to 50 (mBar);
–
Hysteresis equal to 160 (mBar) the theoretical reset point is
900 - 50 + 160 = 1010 (mBar) but this value is out of range.
The reset can be made only by turning the instrument
OFF, removing the condition that generate the alarm and
then turn the instrument ON again;
–
All band alarms use the same hysteresis value for both
thresholds;
–
When the hysteresis of a band alarm is bigger than the
programmed band, the instrument will not be able to reset
the alarm.
Example:
Input range 0 to 500 (°C).
–
Set point equal to 250 (°C);
–
Relative band alarm;
–
Low threshold equal to 10 (°C);
–
High threshold equal to 10 (°C);
–
Hysteresis equal to 25 (°C).
[34] AL1d - Alarm 1 delay
Available:
When [28] AL1t is different from “nonE”.
Range:
From oFF (0) to 9999 seconds.
Note:
The alarm goes ON only when the alarm condition
persists for a time longer than [34] AL1d time but the
reset is immediate.
[35] AL1o - Alarm 1 enabling during Stand-by mode
and out of range indications
Available:
When [28] AL1t is different from “nonE”.
Range:
0 =
Never;
1 =
During stand by;
2 =
During overrange and underrange;
3 =
During overrange, underrange and stand-by;
]
AL2 Group - Alarm 2 parameters
[36] AL2t - Alarm 2 type
Available:
Aways.
Range: •
When one or more outputs are programmed as
control output:
nonE = Alarm not used;
LoAb = Absolute low alarm;
HiAb = Absolute high alarm;
LHAo = Absolute band alarm with alarm indication
out of the band;
LHAi = Absolute band alarm with alarm indication
inside the band;
SE.br = Sensor break;
LodE = Deviation low alarm (relative);
HidE = Deviation high alarm (relative);
LHdo = Relative band alarm with alarm indication
out of the band;
LHdi = Relative band alarm with alarm indication
inside the band;
•
When no output is programmed as control output:
nonE = Alarm not used;
