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4.9.2 – ALARMS HYSTERESIS
The alarm functioning is depending on the alarm hysteresis (par. "HALn"), which works in asymmetric way.
In case of low alarm, the alarm will be activated when the process value goes under the alarm threshold value and will be
deactivated when it goes higher than the alarm thr "HALn" ; in case of high alarm, the alarm will be activated when
the process value goes higher than the alarm threshold value and will be deactivated when it goes under the alarm
threshold - "HALn".
For the band alarms, the example of the low alarm is applicable to the low threshold ("ALnL") while the example of the high
alarm is applicable to the high threshold ("ALnH").
4.10 - HEATER BREAK ALARM FUNCTION (HB)
All the parameters referred to the Heater Break alarm function are contained into the group
“
]
Hb”.
The Heater Break alarm function (Breakage of the heating element) is available only when the instrument is equipped with
the input (TAHB) to measure the current.
This input accepts signals coming from current transformers (TA) with output 50 mA.
The first operation to do, in order to obtain a correct current measuring, is to set on par.
“IFS”
the current that the instrument
has to measure at the end of scale of the input TA (50 mA).
It’s necessary to establish to which output the alarm has to correspond.
To do this it’s necessary to set, in the group
“
]
Out”,
the parameter relative to the output to be used
(“O1F” , “O2F” ,“O3F”
,“O4F”) programming the parameter as :
= Alno
if the alarm output has to be active when the alarm is active while it’s deactivated when the alarm is not active.
= Alnc
if the alarm output has to be active when the alarm is not active while it’s deactivated when the alarm is active.
Enter then into group
“
]
Hb”
and program on parameter
“OHb”
, on which output the alarm signal has to be addressed.
The functioning mode of the alarm is instead defined on par.
“HbF”
which can be set in the following way :
= 1 :
The alarm is active when, with output 1rEG active, the current measured by the input TAHB is lower than the value
programmed on par.
"IHbL"
.
= 2 :
The alarm is active when, with output 1rEG not active, the current measured by the input TAHB is higher than the
value programmed on par.
"IHbH"
.
= 3 :
The alarm is active when, with output 1rEG active, the current measured by the input TAHB is lower than the value
programmed on par.
"IHbL"
or with output 1rEG not active, the current measured by the input TAHB is higher than
the value programmed on par.
"IHbH"
.
= 4 :
The alarm is active when the current measured by the input TAHB is lower than the value programmed on par.
"IHbL"
or the measured current is higher than the value programmed on par.
"IHbH"
, independently by the state of
the output 1rEG.
On par. “IHbL” it has to be set the value of the current normally absorbed by the load when output 1rEG is active, while on par.
“IHbH” the current normally absorbed by the load when output 1rEG is not active.
The programming of these parameters has to be carried on considering also the fluctuations of the net tensions to avoid
undesired alarms.
As regard the hysteresis of HB alarm, this is automatically calculated by the instrument as 1% of the programmed
thresholds.
During the functioning it’s possible to visualize the current measured by the input TAHB when output 1rEG is activated,
pushing key “DOWN” and the current measured when output 1rEG is deactivated, pushing contemporarily keys “DOWN” and
“U”.
To exclude the Heater Break alarm it’s enough to set “OHb” = OFF.
