LEGRAND 1U, Руководство пользователя

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Legrand PDU User Guide 515
In the threshold settings, the Deassertion Hysteresis field determines a new level to trigger the "deassertion"
action.
This function is similar to a thermostat, which instructs the air conditioner to turn on the cooling system when
the temperature exceeds a pre-determined level. "Deassertion Hysteresis" instructs the Legrand PDU to
de-assert the worse state for a sensor only when that sensor's reading reaches the pre-determined
"deassertion" level.
For upper thresholds, this "deassertion" level is a decrease against each threshold. For lower thresholds, this
level is an increase to each threshold. The absolute value of the decrease/increase is exactly the hysteresis
value.
For example, if Deassertion Hysteresis = 2, then the deassertion level of each threshold is either "+2" or "-2"
as illustrated below.
Threshold value Deassertion value
Upper Critical = 33 Deassertion level = 31

33 - 2 = 31
Upper Warning = 25 Deassertion level = 23

25 - 2 = 23
Lower Critical = 10 Deassertion level = 12

10 + 2 = 12
Lower Warning = 18 Deassertion level = 20

18 + 2 = 20
To use each threshold as the "deassertion" level instead of determining a new level, set the Deassertion
Hysteresis to 0 (zero).
Note: The difference between Upper Warning and Lower Warning must be at least "two times" of the
deassertion value.

How "Deassertion Hysteresis" is helpful:
If you have created an event rule that instructs the Legrand PDU to send notifications for deassertion events,
setting the "Deassertion Hysteresis" is helpful for eliminating a number of notifications that you may receive
in case a sensor's readings fluctuate around a certain threshold.
Deassertion Hysteresis Example for Temperature Sensors
Assumption:
Upper Warning threshold is enabled.
Upper Warning = 20 (degrees Celsius)
Deassertion Hysteresis = 3 (degrees Celsius)
"Deassertion" level = 20-3 = 17 (degrees Celsius)
When the Legrand PDU detects that a temperature sensor's reading drops below 20 degrees Celsius,
moving from the "above upper warning" range to the "normal" range, either of the following may occur:

If the temperature falls between 20 and 17 degrees Celsius, the Legrand PDU does NOT perform the
"deassertion" action.

If the temperature drops to 17 degrees Celsius or lower, the Legrand PDU performs the "deassertion"
action to announce the end of the "above upper warning" state.