Hysteresis, User’s guide, Mete red rac k pdu – Dell Metered PDU LED User Manual
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USER’S GUIDE
Mete
red Rac
k
PDU
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Hysteresis.
This value specifies how far past a threshold the temperature or humidity
must return to clear a threshold violation.
• For Maximum and High temperature threshold violations, the clearing point is the
threshold minus the hysteresis.
• For Minimum and Low humidity threshold violations, the clearing point is the
threshold plus the hysteresis.
Increase the value for Temperature Hysteresis or Humidity Hysteresis to avoid multiple
alarms if temperature or humidity that has caused a violation then wavers slightly up
and down. If the hysteresis value is too low, such wavering can cause and clear a
threshold violation repeatedly.
Example of rising but wavering temperature:
The maximum temperature threshold
is 85°F, and the temperature hysteresis is 3°F. The temperature rises above 85°F,
violating the threshold. It then wavers down to 84°F and then up to 86°F repeatedly, but
no clearing event and no new violation occur. For the existing violation to clear, the
temperature would have to drop to 82°F (3°F below the threshold).
Example of falling but wavering humidity:
The minimum humidity threshold is 18%,
and the humidity hysteresis is 8%. The humidity falls below 18%, violating the
threshold. It then wavers up to 24% and down to 13% repeatedly, but no clearing event
and no new violation occur. For the existing violation to clear, the humidity would have
to rise to above 26% (8% past the threshold).