The hysteresis is the difference between the value where the alarm turns ON
from turning OFF and the value where it turns OFF from turning ON.
This difference is defined in % of full scale. In figure 10 an example of a 50%
threshold value high alarm with a 10% hysteresis. The blue line in the top graph
reflects the gas flow, the vertical dotted lines the switching points.
The blue area’s in the graph below is where the alarm is activated. The reset is
set to automatic.
Figure 10: Explanation hysteresis
Please note that you can enter a value of 100% as hysteresis value. If
you do that the alarm will no longer switch off.
Alarm delay (Default: 20ms)
The alarm delay is a delay in milliseconds between the moment the alarm
situation occurs to the moment that the alarm is activated. It can be set from 20
to 9999999 msec (=2.777 hr).
Alarm duration (Default: 500ms)
The alarm duration is minimum time that the alarm is active after it is activated.
It can be set from 100 to 9999999 msec (=2.777 hr)
Note: This function is only active if the reset is set to automatic.
Reset source (Default: Manual)
The alarm can be reset in different ways. Below a list of the 4 possible settings:
Automatic
The alarm is reset the moment the alarm situation is no longer valid. This
unless you programmed an alarm duration. For a totalizer alarm this
setting will reset the totalizer as soon as the threshold has been
exceeded.
Manual
The alarm stays active until you manually reset the alarm through the
touch screen of the flow meter.
Input 1
The alarm stays active until you activate input 1
Input 2
The alarm stays active until you activate input 2
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Rising edge
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Falling edge
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Both edges
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High level
□
Low level
Reset trigger (Default: Falling edge)
(Note: this function only relates to alarm reset by input 1 or 2).
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When you use input 1 or 2 as an alarm reset, you can set exactly on which
action the alarm is reset. If for example the input is a manual push button, the
rising edge is the moment that you push the button and the falling edge the
moment when you let go of the push button.
Please note that the reset overrides the alarm. Even if the alarm is still
valid, if you set this reset trigger to high level, the alarm is ignored until
the level becomes low again.